Shower repair

Monkey1708

Hi all,

The cold tap on my shower will only work if the kitchen tap is on. I have changed the microswitches, but no joy. 

I've swapped the wiring over and even tried the hot water pipe on the cold tap of the shower, so I know it's not the shower unit itself. Now I'm totally stuck!

I have been using on site facilities, but this year I'm feeling more adventurous and would like stay at CLs which don't have such luxuries like a shower block.

Any ideas as to what to try next to fix my shower is much appreciated.