Mate, i would use copper all day long. I had an extension built and plastic push fittings were used. Well so far 4 have them have let go including the hot feed for the kitchen sink. This caused my boiler to fire up over night and the hot water ruined a new kitchen which had to be replaced.

I know a lot of the heating engineers like plastic but I hate it. I had to get my dad round to change it all back to copper.

get it done proper, get it done in copper..ooh quite catchy that