Sparkplug caps and blipping issue solved thanks to Bill Smith's Triumph in Chester. The sparkplug caps were arcing when the engine got hot, making it jerky and a bit dangerous to ride in stop/start traffic. The issue has been acknowledged by Triumph and the bike now has a shiny, new pair of plug caps with more insulation.
Triumph have also issued a recall regarding the blip stall issue. Basically if you blip the throttle at tickover, the bike would occasionally stumble and even stall. This, combined with the sparkplug caps meant my bike seemed to be getting gradually worse to ride in stop/start traffic. The fuelling map has been adjusted and my bike feels great now 😁
Please excuse the muck! The roads are drying out around here but there is so much muck and salt everywhere 😕