Nice plan!
Went in to see Alan yesterday. Next project - replace the rusty, horrid cat-back downpipes with some more of his stainless - and he's going to do something with remote controlled bypass valves, so that when I want, by thumbing a button in the cabin, I can get a monster straight-through pipe noise, bypassing the silencers completely, but in normal driving, sounding as it does now - civilised.
All a bit experimental, but I like this plan. And over the winter, he's going to have the wings off and start working on some proper tubular manifolds, to replace the standard BMW items and hopefully free up some airflow (also fitting sports cats, as the final touch).
Shall update you all on progress when it all gets done!