You have a few issues to consider.
1) UK Hiltons are very poor, especially outside of London.
2) Some 3rd party bookings may not get you HHONORS Gold benefits, depends on the 3rd party. The bed preference also needs to be confirmed by Hilton.
3) Hilton is weaker than other chains in guaranteeing room type and bed preference. Hyatt actually guarantees bed preference booked.