Glad it was something minor in the end, Nathan. Had I been driving a Laptop with TIS rather than a barbecue and a half-empty bottle of plonk when you phoned I might have been more use.

Fuse 15 feeds all sorts of circuits - seat and mirror adjustment, seat heating, self-levelling, headlamp levelling, reversing lamps, MID/CID and phone, the engine cooling relays (but not fans), wiper rain sensor, anti-theft system...
Most of these circuits draw their main current from a separate unswitched supply so are unlikely to blow this fuse in a "normal" failure mode but notably the seat heating doesn't appear to. :-/
Do you remember anything odd happening when it failed? Anything that might have activated one of the above circuits?
Of course, it could be that this fuse is run fairly close to its' rating and failed due to fatigue.
Kevin