Now, how would I connect fixed pipework to the fixings? The outlet/inlet
is a plastic 3/4" male thread. Should I be using a 3/4" tap connector,
3/4" female iron and PTFE or something else?

I recon some of those braided hoses would work fine.

I need full bore, though, really. The entire house, hot and cold is mains
pressure. I'd prefer to do the pipework in flowed 22mm pipe.

Christian.