Our CH, is a combi boiler feeding 2x22mm copper pipes which branch at a T for upstairs & downstairs. I would like to add 3 new rads in the conservatory, the boiler has the capacity to take them, but I would like to know (a) is it OK to T- off the 22mm downstairs or do I have to go from the last rad in the line?(the end of the 22mm) It is about 8 metres to the new rads from the existing pipework. (b) Is plastic pipe OK for CH?(c) Are push fit fittings OK for central heating?(d) Anything that I need to be careful of? Many thanks.