The problem in the UK with the US 45-deg to downwind join is that it is illegal at an airfield with an ATZ. Without dragging out the ANO (I'm sure someone will find the reference) I am 99.9% sure that it states 'all turns within the ATZ are to be made in the circuit direction'. By definition a 45-deg join requires a turn against the circuit direction as you enter downwind.
FWIW I like the OH join and I'm not that much of a fan of the 45 deg one - I've flown both quite a bit and hold a US PPL as well.
Tim