Thankyou for all your help!!
The gate valve no longer leaks and I shall be leaving that well alone now!! I have traced the cold feed upwards and there is a compression join with an isolation valve at the top of the airing cupboard wooooo!! Quarter turn clockwise should do the trick hopefully.
Still have no idea what the extra pipe is for as I dont have a mixer shower but I see your point. I have an electric shower which is fed through the bathroom ceiling from the header tank - I wonder if previous owners used to have one on an older suite and maybe its end capped somewhere althouhg I cant think where?
The pipe still gets hot though so god only knows.... any other ideas?
You have all been a massive help and I feel like I fully understand how all this stuff works now!
