Well, fitted the plugs last weekend with some supervision from tracee's old man and the car is running sweeter than ever. All the jerkiness at low revs has completely gone. Haven't seen the injector light again either.
Man, those centre plugs are in tight aren't they? We destroyed a plug wrench trying to get the buggers out. When they did come out they were still in good nick and presumably still the original ones at 64k miles. Only one problem, some oil in one of the plug wells - likely to be the cam cover gasket?