Sorry to bother again - had some good responses to question on venturi showers and some comments about electric ones.
Off to see the house tonight and I have started to think Electric - mounted in roof space. A neighbour has one - but it is a very expensive bells and whistles one. The location of the heater unit seems to make good sense to me as I don't need to think about neat piping or wiring. I could just tee off the cold feed to the loft water tank and (hopefully) find a good route for a suitable cable. (I would get an electrician to complete the wiring) Question: Any suggestions for such a loft mounted electric shower? I haven't seen any (apart from my neighbours) - but then they wouldn't look very attractive on a display I suppose. Any ideas why the range seems so limited - given that most bathrooms have roofspace above?