Firstly, thanks guys for the tips and advice, it's much appreciated.
I've double checked the soldering on the warning lights that was redone a couple of years back and it appeared to be ok. Just to be sure, my brother in law resoldered them for me in about a tenth the time it would have taken me (and neater too!), and the engine warning light now works again!
Before that though, I was a little surprised to find a few bulbs out on the outside of the car, especially given she's only just passed her MOT two weeks back. One brake light was out; quick change and the MIL has gone out (I'm sure I've had a brake light go before now but I don't recall the MIL coming on, my memory must be rusty), so no need to check the diagnostics.
However, in removing my battery to replace a blown side light, I sheared off the clamp bolt Seems to be one small annoying thing after another for me atm!