Scirocco Register

So you may or may not have heard about the red shed melting the top of its rotor arm on the way to Tatton Park last weekend, managed to get it home on a 2nd hand rotor that wasn't an exact match but have since put a brand new correct arm in

However, despite running ok-ish on idle, it sounds lumpy and slightly laboured on revving, leads/cap/arm are new, going to replace the plugs this weekend, if that doesn't work, is it new dizzy time? Or is it just the ignition timing has slipped out?

Could be the plugs fouled during poor running so replacement is first call.
Cant see the timing 'slipping' in the circ's you describe. Once you do the plugs if there is still an issue test the hall sender and the ign' module as per the Haynes book of lies....

check the coil isn't tracking out.
i had a burnt out rotor once and after i replaced it i had a lumpy idle and misfire.
when it was dark you could actually see the spark tracking from the coil turret around its base (it had cracked in the heat) and jumping to the negative terminal.

Picking up some new plugs in the morning, Bosch WR7LTC+ ones, can get four from GSF for £11 whereas the NGK BUR6ET I was using are £25 a set so will start from there really, the only things that have changed are its run on a knackered and slightly different rotor arm and the caps been off four/five times so am hoping its just what duggers said and that the plugs have fouled up

New plugs done the trick, sweet as a nut again, cheers for the assistance boyos

That's good news.
I have a saying I use when delivering the training I'm involved in; If it quacks and it waddles guess what, its a duck.

Sometimes simple is the answer.

Bosch plugs for a DX engine should be WR7DC+. The tip of the "L" is totally different (and they are twice the price!).

I stuck with ngk's in the end, it seems to like those