The funding for Team GB is basically for the Olympics, the athletes train to peak every four years and are paid by the British Olympic Association out of Lottery money set up by John Major after the disastrous Atlanta Olympic games though the excuse was to fund good causes. The amount of success depends on the Olympic Association's thoughts on which sports the medals could come from and how high the chances are, hockey being a team game has 11 players plus reserves and to pay them ( some part time others full time) is expensive, boxing is simpler as there are amateur competitions and the best are chosen for funding.
Some sports have expensive equipment like sailing and cycling, way back in the 60's when the UK sport was all amateur Rodney Pattinson was racing in the Flying Dutchman class, I was a young trainee submariner Tiff and we were asked to volunteer to make fittings for his boat as the cost of titanium fittings were almost unaffordable, we made various shackles, rudder mountings and general deck gear from various titanium extrusions by hand, Rodney at the time was a Lieutenant in submarines, he won, but in those days many of our Olympians were service personnel as that was the way round the amateur rule, the communist block athletes were all members of their armed forces, the USA tended to be college athletes or coaches from different disciplines ( you can't be paid in the chosen sport but can in other sports). The reduction of our armed forces and sports funding to the forces equipment reduced our Olympic success until it became Olympic failure in Atlanta.
Olympic success is expensive and billions are thrown at it for national pride, whether you think this is correct is immaterial, competition costs, whether in development or equipment in any sport, Mercedes pay the UK billions of pounds to be a successful German team, the Gulf States pay McLaren billions to be a successful British team and the Austrians pay billions to the UK to be a successful soft drinks company, it doesn't make sense but it is the way of the modern world, I wonder which team the Chinese will buy.