I've worked with athletes in the past and they get paid good until they are no longer needed which is as soon as they reach their 30's but their clubs or sponsors pay them, the national team don't unless they win a gold medal where their country (sports ministers) will hand them a good prize money.
Normally they earn peanuts until they reach their early 20's and earn good until they are no longer needed in the squad. I personally know a few of these athletes very close where one was injured in the knee and had to retire at 25 and a few left at the age of 33 which are now trying to come back to the sport as a trainer or some sort of manager as they don't have a plan B to go to and make money for the rest of their lives.
Only a few athletes will become the poster faces for advertising purposes and will have decent sponsorship but that's about it, then they have a lifetime left after their 30's to live with whatever they have earned or invested in. If I'm honest, I don't admire that sort of lifestyle as they train so hard from a young age and miss out a lot in life, only to make money in their prime time and then get tossed to the side. Some of the athletes I know were also studying part time as they want a second career to fall back to as soon as they retire.
I have a lot of experience behind the scenes of this particular sport in the Olympic games right now and that's from a different country so I can't really comment on Great Britain but I'm assuming it's roughly the same everywhere else. It was very difficult for me to manage these athletes as I worked in the marketing and sponsorship field. The federation wanted to boost its presence to gain more sponsorship to fund the sport (national fed needs money), the athletes hated taking part in any extra activities as they are either training or participating in tournaments and there I was the in-between person trying to keep the relationship sweet and try to get the athletes on board. If they don't participate, slowly they will be eliminated from the national squad where their dreams to compete in the Olympics would be crushed and in order to compete in the olympics in the first place, the athletes must compete in many international tournaments and win their place in their continent. So if you're in the national squad in the European continent, you have Russia, Serbia and many other strong opponents to eliminate before you can take your place on the Olympic stage and there's only 2 tickets to win as a country. If you can't win one of those tickets, then you have to go through all of that for another 4 years and unlucky for you if you have hit your 30s as you won't be on the squad for the next olympics.
The sport I worked in is a very popular team sport across the world but not so popular in the UK but the athletes are very lucky in this sport as the federation does all the funding through sponsorships and grants they get from the Ministry of Sport in my home country unlike most athletes in the olympics right now particularly solo athletes who don't get any help at all from their countries where they have to do all the work themselves to fund their dreams.
There are many athletes out there right now competing in the olympics where their home countries won't even pay the license fee to broadcast their athletes on their national TV's competing for their country even winning medals let alone sending a national press team to cover their own athletes.