England, Scotland and Wales will be represented, though the other nation in the United Kingdom -- Northern Ireland -- will not take part because the combined Irish teams did not qualify.
Other countries competing at Rio 2016 have been preparing their squads since last year, but Britain's men's and women's coaches Simon Amor and Simon Middleton have only been able to work with their combined groups since the end of the respective 2015-16 Sevens World Series competitions.
"It's been a tough year as England's sevens coach, with very much the Olympics being the focus and constantly looking at the Scottish and the Welsh players as well as managing my own," Amor told CNN's World Rugby show
"But now to get this many talented players here together in this one Team GB and creating an amazing spirit with Rio on the horizon, I'm very, very proud and very, very excited.
"It's been a great challenge. We set our sights on creating an extraordinary Team GB spirit."
While the London 2012 men's football squad controversially omitted Scottish players, Amor's Rio team will feature all three nations.
England, which finished eighth in the world series, contributes eight of the 12 while Scotland -- 10th overall after winning May's London finale
-- has two, as does 12th-placed Wales.
"There have been no negatives -- completely positive," says Welshman Luke Treharne, one of the two traveling reserves along with England's Ruaridh McConnochie, who has Scottish parents
"From day one the boys were getting to know each other, having a good laugh and chatting about past times they'd played against each other where maybe something has gone on in a game.
"The Team GB spirit has come together really well. It's nice to finally get to know them and become friends with them."
Gavin Lowe was one of the Scottish players at the training camp who missed out on a place in the squad.
"The mood has been really good, on and off the pitch trying to gel as a team," said the 21-year-old, who had six weeks out with an ankle injury before the camp and has subsequently had surgery ahead of the new UK season.
"Off the field we're doing a lot of activities, trying to mix it up, always trying to sit with Welsh, English and Scottish boys all at the same table -- just getting to know everyone."
Treharne was one of the captains as GB entered two teams in the Moscow, Exeter and Gydnia warmup tournaments -- they played each other in the final of the concluding event in Poland.
"It's a massive benefit having three different countries coming together. All three countries play in slightly different ways," the 23-year-old said.
"As we saw in Moscow there were times when we clicked really well together, and times when you could see that the boys were used to playing a certain way for their country. But as the tournament went on over the few days you could see that the team started gelling together really nicely."
The GB men will be led by England captain Tom Mitchell, while compatriot James Rodwell is eighth on the all-time list of world series appearances with 308 after playing in a record 69 consecutive tournaments.
The squad doesn't have any top-level stars of the 15-a-side game, but features try machine Dan Norton.
"We've got an amazing bunch of boys, a great level of skill as well. We all want the same thing -- we all want to win that gold medal. We've got enough talent in the room," Norton, who is sevens' fourth-highest try scorer on 210, told CNN.
"We're playing against these guys all the time and sharing a hotel with them, so it's not too far from being enemy and friends at the same time. But we're all pushing for the same goal. The hardest thing is getting us all used to each other in such a short time."
Amor said the training camp was designed to get the players in peak physical condition, with the Rio schedule requiring six 14-minute matches played over three days.
"It's the most competitive environment I've ever been involved in. And that's what it needs to be -- every day, every single session," said the former England captain, who was the inaugural world sevens player of the year in 2004.
"Sevens really isn't rocket science -- it's an amazing team sport where your skills and your team ethos are put under complete and utter pressure through fatigue and exhaustion. That's how you train. The boys train above the demands of a World Series game.
"Only those who've got unbelievable fitness levels and have the desire to inflict constant pain on themselves really do succeed in this game. It's a special type of character that excels."
Fiji goes into the men's tournament as a clear favorite after winning back-to-back world series titles
, but many teams have genuine hope of a medal given last season's unpredictable results.
Lesser powers such as Kenya
and Scotland pulled off big shocks to win titles at the three concluding tournaments, though Fiji and fellow heavyweight New Zealand both lifted three of the preceding seven.
"We're under no illusions that we're facing an enormous challenge given the lack of preparation time we've had compared to all the other nations," said Amor, whose England team reached just one series final -- in Dubai last December.
"But we're fully aware that with the talent we've got and the incredible Team GB spirit, we can surprise a few people.
"We've got some incredibly talented, agile, fast, game-breaking players in our team which will make us an exciting, attacking kind of side."