I've stayed in all three wings over the years. I find the hotel reasonably casual and whilst I don't recall there being any dress restrictions I doubt you'd be too out of place in smart tailored shorts.

Valley wing definitely the best, but quite pricey. But difference between that and a Horizon Club room in main wing might not be that great, if so it's a no brainer! Private Breakfast room, top class rooms, butler service, all day drinks including Champagne etc. Still reasonably casual.

Garden Wing - quite like these - very tropical and quite spacious. Think they've introduced a club concept since I was last there, not sure.

Tower Wing - the main wing of the hotel and 5 star but not luxury. If I were to stop in this wing I wouldn't stay in anything smaller than the executive or premier rooms