Just put a set of Splitfire plugs in (bought on eBay).
Also changed oil and filter, thought I'd try Lucas 20W50 (for camchain noise).
Also replaced the 3-way coolant hose joint that broke apart recently.
Bike now feels extremely smooth (for a 21-year-old), cam-chain rattle slightly quieter too (when warm).
However noticed a bit of clutch slip at very high revs, could be normal wear (lot of London commuting) rather than oil-related.
Anyone else used these plugs / this oil?
Also, if you're in need of tyres (bike and car) or service in the Kingston upon Thames area, try Kingston Motorcycle centre Hampden Road KT1 3LG. A new business run by a bike expert (has been a mechanic at the TT), he deserves to make a go of it so give him your support. Tyres seem keenly priced and he knows a lot about bikes.

 

I have Splitfire plugs , not a bad plug and yeah 20/50 helps in the short term until the
oil wears a bit.

Betting you got the plugs from Abbey in Leicester !

 

Yep, Abbey