Just had a couple of very nice and very expensive Stelrad vertical radiators installed but they're off-puttingly noisy when the central heating fires up - it literally sounds like a trickling tap into a metal bucket from a great height. I've been told this will settle down and I might need to bleed the system a few times (which has been done) but it's still very noisy. Anyone else had this issue and does it indeed settle? It's reassurance I guess I'm after given the expense involved. All the rads in the house are regular type, basically new, virtually silent, the boiler is a 11 month old Vaillant Ecotec Combi and there are TRVs fitted throughtout.