The Radisson is one of very few hotels in St Helier that will GUARANTEE a room with a walk-in shower (and grab rails etc) if it's available at the time of booking. The L'Horizon Hotel in St Brelades has the same.
Many other hotels have some rooms with walk-in shower but won't guarantee one until you get there; useless if you can't manage without. Lots of them, being older buildings also have steps here and there, even in the middle of corridors at times.
Unfortunately as someone has mentioned, disability access laws do not exist here, so most hotels have not adapted.
It really depends how important it is to you as an individual. I once had a lady who couldn't manage a bath book the Merton Hotel - they don't have walk in showers but they do have lift and ramp access to everywhere and fully equipped swimming pool changing rooms, which is where she took a shower everyday! There are ways and means... :)