Who ever you use...when you actually see them at work...up and down the stairs sweating like mr jackson in a play ground, it will seam fair... and besides, your paying for what he knows as much as what he does...hope you get a good price and good service. P.S/ average upgrade price in Brum is around £1750-1850. Thats removing old boiler, cylinder, tanks etc. Installing Vaillant Ecotec Pro 28, Integral clock, honeywell stat & 7 TRV's.