Thanks for trying to help but I don't think your suggestion will work. the one new board may replace the two original boards from a functional point of view but the control board in the old arrangement fixes to the front panel of the shower and has the push buttons on the board which poke through the front panel of the shower so that it can be operated. Indeed, if you look at the link that you posted and then click on the description of the new PCB the web page specifically advises to make sure you are ordering the same part number.
Once again though, thanks for trying.
Steve