Hi and thanks for all the responses, and sorry bit slow to get back (dont ask). The mixer valve (Hansgrohe) has internal BSP connections, and was not supplied with any outlet fittings or seals. I've followed this up with the suppliers, who arent being very helpful. I'm using elbows, BSP to compression. The compression end connecting to the pipework is fine, but the end screwing into the valve is difficult to seal. I dont think you are meant to use sealing washers, and in any case couldnt really with an elbow, cos it wont neccesarily screw in to the correct depth when the elbow is correctly aligned.
Actually since posting, I've done this with a few extra winds of tape, (definitely winding it right way) and it seems to be OK. Still not convinced though. Maybe you could use straight outlet fittings with seals, then elbow after?
Have tried to upload pic, but cant work out how. Have also trawled hansgrohe website - no obvious clues there, and cant find installation instructions anywhere online.