Croft; are you actually gasbusters on Diynot?
Don't blame the punter FFS: he has no idea what a job should cost, or how it should be done, and , anyway, the real cowboys charge over the odds and do work like this.
I cant be arsed to look beyond the first photos or properly read all the inane comments. (Apologies to those who provided sensible contributions ). I am not a qualified plumber,but a Gas Service Engineer, but I know the hot should not be run off the horizontal vent/hot supply. Obviously best to use a flange, but otherwise break into the vertical hot supply, before any other draw offs. The cold feed is not clear,but should be taken from the CWS, below the cylinder supply connection,
The job is a mess,but don't blame the punter who presumably pais ££££'s for the crock.