I think if you have offers from Epsom and Shrewsbury, you are pretty solid academically. They are both good schools, I know a family whose both sons are music scholars in Shrewsbury, and are very happy with the school.
My nieces all went to Epsom, all gained straight A and A* and all now in RG universities. From what I heard, both schools are good. Sorry, don't know much about Warwick.
First of all, have you visited any of these schools, if you are going to board for your A level, you need to check out the boarding facilities, and school environment. Both schools have overseas students, so you won't be the only one. And where do your guardian live, or do you need the school to arrange one for you. You need to have a feel of the school and talk to the teachers and housemasters.
Shrewsbury, you will be flying to Manchester, whereas, Espom you will fly to either Gatwick or Heathrow. I think they may have National express bus from Heathrow to Shrewsbury, you need to check the bus route. But it will be a very long ride nearly 6 hours and change in Birmingham, So logistic nightmare, but Manchester is a closer airports and have direct flight to HK.
Espom is a lot closer for Int'l flight transfer and more airlines have flights to these 2 airports from HK. It is a good school, and strong for potential medic, and what I know the boys and girls do study hard and play hard, my nieces are no bookworms they love their parties, but they all did well and gained great results.