So update on this one now the car has been to the garage:
1) White smoke: Did your test, no smoke so I assume it was nothing abnormal and is instead me being a bit paranoid.
2) I got them to check out the wheel issue. The challenge was tire feathering (abnormal wear) which was causing the road noise on front right. They've moved it onto the back to try and reduce the noise, but a new tire will be needed at some point. My MOT is in May so I plan to get new ones before then; as you say, they're reaching the end of their life soon in any case.
Thanks for your help on this!