Removed all 4 wheels this weekend to see which of the pads was setting off the warning lights, and almost part of my thumb too as all of the caliper bolts bar one are seized. (Nurse at local hospital all sympathy once she realised the Saturday night deep cut was not drink related). The rear pads are completely trashed but are not wired up, the front pads which are setting off the DIS warning light have still got 4-5mm left. Regular inspection required there. I also found that the security bolt from the left rear was missing, which goes some way to explaining the persistent vibration since the tyres were changed. Whether this is cack handed Kwikfit not retightening the bolt after the tyres were replaced, or the bolt was missing and they never told me i cannot prove, but i am mightily pi22ed off.
I think heating up the bolts is probably the only way top get them undone, but as eveything is soaked in penetrating oil now and i'm one handed for the week, it'll have to wait.