There are three categories coming out here. The first is what IanXC was actually thinking about - and is fairly rare. Platforms where HSTs regularly call which could be described as 'bays'. Aberdeen, York and Leeds have all been mentioned many times and they regularly take 2+9 HSTs (although only
just at Aberdeen

). The rest are mostly bay platforms that have been set up to take 10-12 20m commuter EMU vehicles mostly, and are typically in places HSTs have never ventured. Often these just happen to be bays for some reason and in some cases these are bays by accident more than design (like at Portsmouth and Southsea). I suppose a final category takes that one step further to include places like Manchester Piccadilly and London St Pancras - where it really depends how far we're willing to stretch the definition of a bay in order to include them.