Manifold/EGR valve replaced today by local dealer. Job took just over 3 hours. First iQ they've had in for fitting of the replacement parts on this 'campaign'.
Can't say I've detected any improvement in drivability, but ours was never bad anyway, and have been using Redex regularly for the last 18 months.
Important to me is that I no longer have the worry of a £900 repair bill hanging over me should performance have degraded at some point in the future due to clogged EGR valve. So a feeling of relief that this 'ticking time-bomb' is now resolved without any cost to me...
Dave