Thanks Terri and Fren,
OK so I'm going to keep it quite wet from now on, I'm more comfortable with doing that in Hydroton than I was in it's old pot, simply because I had no idea what it was actually in (how much was bark and how much was rock wool as I could see one at the top, the other at the bottom, with no idea what was in between).
Fren you are probably right that it would have been fine in the rockwool but I didn't realise it was mostly that until I had already broken the existing pot trying to get it out, I thought it was in mostly bark and was uncomfortable about that (and underwatering as a result).
Anyway, good to hear they are quite versatile, and Ray has had good success with this same orchid in S/H so I'm going to go for that.
Thanks again everyone