The bathroom wall that the existing Mira 8 shower is fitted into backs on the the wall of the airing cupboard down which the main pipes run so I suspect that it will be a straightforward job for a plumber to fit a replacement. (Mira no longer stock spare parts for it)
My query is for help to identify a suitable replacement that will span the 6" diameter circular hole in the wall, preferably without the need to cut the tiles. Nothing too expensive - we are getting on and whoever buys the house will do a complete refurbishment.