Thanks for your help and advice - you were right - supply fuse is 60A - I'm hoping REC will uprate it when I have the isolator fitted in VNF.
60A (14.4 kW)seems a bit light nowadays ? It wouldn't take many appliances to push that surely? Thinks - WMC 2.5 kW, TD 2.5 kW, DW 2 kW,mwave 1.5...