In the US, I know that there are heaps of opportunities for student athletes - scholarships, help with admission etc. Is this the case in the UK too?
No - while competing in a sport such as rowing will help you get into a university (especially if you are on the boundary line in terms of academics), there are very few sport scholarships from UK universities.
The most competitive British Universities do not offer opportunities for sport scholarships, and no sport (not even rowing) will give you an advantage when it comes to gaining admission to a top UK university. The focus is very much academic, and if you happen to be a good athlete too it’s a bonus but not one that will in any way help you get into a UK institution. If anything, drawing too much attention to sport in your application will disadvantage you, because they will be concerned you will spend time doing sport and not working, so the general rule for Oxbridge, the University of London and other Russell Group institutions is that sport will not aid your application.
Hope this helped!