We had to replace the Ball cock in the Header Tank. We switched the water back on and kitchen cold tank spluttered a lot but is now working fine but shower isn't. It is just trickling. We have tried running it for a while to clear any air locks but no luck. Any ideas?

When you replaced the ball cock you disturbed some crud or mineral build up on the pipe walls and it got sucked up into your shower and is now blocking the inlet ports of the cartridge or the supplies. The answer is to turn off the water to the valve and open it up. Check the inlet ports for trash and then turn the water back on for a few seconds to flush out the supply lines.
You should have a full stream out of the supplies before putting everything back together. Good luck, Tom

Will give that a try. Thanks.

Hi Claire,

I should have advised you to first remove the shower heade and check it for blockage. I apoligze for the omission. Tom

We had already tried that so no worries. Just wanted to let you know that we followed your intructions and sure enough it was full of gunk, and is now working perfectly. Thanks a million.
Claire