Not a spare seat was to be had at St Michael and All Angels' Church in Croydon on Monday as mourners – some travelling from overseas for the service – packed out the church.
A moving tribute from the 22-year-old's mother, Diane, was read on her behalf by Father Ian Brothwood - the vicar who baptised Stephen at a young age.
The eulogy told how Stephen's Thailand trip had been driven by his yearning for exploration and experiencing the great outdoors.
"As a baby, he would be climbing out of his cot before he could crawl. It seemed he could run before he could walk," the congregation heard.
"Apart from his sport, he didn't take school very seriously and was always looking out of the window. He wanted to be outside. He preferred the university of life to formal education."
It was this love of being outside which led to Stephen taking up football from the earliest age possible, playing for his school teams before going on to have trials for Crystal Palace and West Ham.
It was also why he took up golf, securing his first-ever hole-in-one at the "mature age" of 13, later becoming a player with a handicap of five.
The 300 mourners also heard the importance of family holidays to Stephen, which he had enjoyed with his mother, father John and sister Emily.
They heard how he and his sister had gone to catch mackerel in the sea, only to be told by their father, who had owned Upstream Fisheries in Wallington, they wouldn't catch any, but that if they did, he would gut the fish for them.
Father Brothwood added: "But they started to haul them in and John had to sharpen his knife so that Diane could cook them.
"He was a leader, not a follower. He loved the good things in life. He was fun-loving, but it wasn't all one way because people were also able to laugh at him too.
"Stephen packed a huge amount into his short life, and right to the very end, he was having the time of his life.
"That's why it was so tragic that as an innocent bystander, he was caught in the crossfire of the violence and evil of others. He was in the wrong place at the wrong time.
"Hopefully there will be justice."
Stephen was shot dead while seeing in the New Year in Thailand with friends on the island of Koh Phangan. He was caught in the crossfire after a gunfight broke out between two rival gangs.
The cortege was led by funeral directors Rowland Brothers, who also arranged for the repatriation of Stephen from Thailand.
Pallbearers carried the coffin in front of his grieving family as the service got under way.
A floral tribute alongside the 22-year-old's coffin read "Big Hands" – the nickname he was known affectionately by among his friends, and which schoolmate Glen Thomas, who gave a personal tribute during the service, made reference to in his speech.
Mr Thomas said: "He was someone who lived life to the max. Everything was big, from the nights out to the size of his hands. Everyone who met Steve loved him.
"He was having the time of his life [in Thailand], he was living the dream. He went cliff jumping, he swam in the clearest blue sea, he rode an elephant, slid down a waterfall and even managed to share a beer with a monkey.
"He met and befriended people from all over the world, some of them who are here today, which shows how much of an impact he had on people. He loved his family and wanted nothing more than to see his sister succeed.
"He was a clever and ambitious young man. I feel privileged to have had the opportunity to know Steve and have memories I will cherish for the rest of my life."
Stephen's childhood friend Karl Mason paid tribute to his ability to "excel" in everything that he did.
Mr Mason's tribute, also read by Father Brothwood, said: "My first emotion was anger at the cutting short of such a promising young life. Stephen was my best friend, and losing him in such tragic circumstances is like feeling a part of me is now missing.
"What I take comfort from, are the many fond memories of the times we had."
Mr Mason talked about Stephen being the life and soul of the party and recalled how he would check his hair "on every single reflecting surface" while on nights out in Croydon.
He also paid tribute to how former Riddlesdown Collegiate student Stephen, of Verulam Avenue, Purley, supported his family after his father John died from a brain tumour in 2011.
Mr Mason added: "It didn't matter if it was just one other person or a big group, he was always up for a night out, and someone would have to put up with his suspect dance moves.
"Stephen's life may have been short, but he made every moment count and made a lasting impression on many people's lives.
"My best friend, it has been an honour.
"You may no longer be with us, but you will never be forgotten."
Following the 30-minute service, Stephen's body was taken to Croydon Crematorium.
A wake was held at Addington Palace Gold Club.
The Ashton family are asking for donations to the Seve Ballesteros foundation, supporting Cancer Research, which can be made online here. A family statement on the donation page reads: "We know that Stephen would have wanted any monies donated in his [father's] memory to go towards brain tumour research and any project that could lead to advancements in the treatment of this cancer."Stephen's mother Diane spoke after the funeral of how 'proud' her son would have been of the service in his memory. Mrs Ashton, who also tragically lost her husband to a brain tumour in 2011, said her much-loved son would have been 'having a chuckle' at some of the stories shared about him. She said: "He would have been proud and it was no less than he deserved. "He would have been moved by all the people there which included his friends, family and work colleagues. "He would have been laughing at hearing people recalling the stories of him and having a chuckle. It reinforces what you already know about your own son, about how well loved he was. "I was really moved with the service and the numbers of people that were there to support us and share the memories. "We were overwhelmed by that. For us as a family, it helps us in still trying to come to terms with our loss but it is still hard moving on." Mrs Ashton also said how 'difficult' it is for the family to only be able to watch what is happening in the fight for justice from afar. Thai national Ekkapan Kaewkla, 26, is in custody in the country but is still to be formally charged as prosecutors decide whether to cite him for manslaughter or murder in a trial. He can be detained for up to 84 days before a decision is made. The family are being assisted by the organisation Missing Abroad, linked with the Ministry of Justice's National Homicide Service and the Foreign and Commonwealth Office. Mrs Ashton, 48, added: "It is difficult for the family to follow from afar what is happening in Thailand. "Over here you put your faith in the Crown Prosecution Service and we know what the English justice system is. "But in Thailand there are differences in the legal process and obviously it's difficult knowing how the case is going to move forward. "It's still early days and we are awaiting news on any developments in Thailand before we make any further decisions. "For us, we want justice for Stephen. "We want to be confident that due process of law will happen. "We also want safety measures in place and enforced that would protect other people who go over there. "That's very important to us as a family." Since the shooting, local politicians have declared the island will be made a 'gun-free zone' within a year, a move described by Croydon South MP Richard Ottaway as the 'minimum' that could be done.