R
RPG 80
Firstly if you can find a second hand boiler and a gas safe engineer willing to fit it, you have no guarantee and recourse if the appliance packs up once the guys walked out the door and that's not including the safety implications of fitting a second hand appliance. You are on a hiding to nothing really as no engineer will give you a quote without visting the job as there are to many variables to guess via the forum. Your best bet is to get a heating engineer (gas safe) round and explain the situation and make an informed decision on the best way forward. Then get two or three written quotes for a new boiler and joining back onto your central heating. good luck