Update on this, but first off, Joff you have a pm, re spare injector hoses and nozzles if you need them.
Turns out, they had drilled the nozzles on the angled inlet pipes on the manifold, rather than by the petrol injectors as Kevs guide. This meant there was nowhere else for the pipes to go except over the fuel rail. So as we know there no room for a pipe to pass through there, when the plenum was re fitted, it squashed 3 of the pipes and upset the fuelling.
Pot 6 was exceptionally bad, as t had also crushed the fuel pipe over the fuel regulator vac pipe as well, so pot 6 had no chance, hence the agro on that cylinder especially.
The nozzle position will have to be drilled and new/other nozzles fitted if the old ones brake off on removal, they're only brass ime anyway. Although we couldn't see what the installer had used.
Anyway, got some bits here if your not already sorted Joff.