I've been plumbing for 23 years since leaving school, and I use Hep2o plastic pipe where it won't be seen and copper on any surface pipework

Never ever had issues with the plastic, as long as you use the sleeve and its pushed in fully you wont have a problem

Use the "barrier" pipe for heating pipework btw

Other Plumbers will say different makes, but I personally have found Hep2o best