Thanks Guys for the advice. 15mm it is with isolating valves fitted at the tapping point.
Useful info about the door needing to be exterior quality , didn't know that.
Thanks
Dave
I have an existing system which is working very well. Condensing boiler, pumped system ,conventional indirect hot water tank in airing cupboard, rads in most rooms. My question is I would like to add a radiator in my conservatory. The existing system is 15mm but I would like to use 10mm...