Just spoken to someone at NFS Regent Street.

I got as far as "I bought an N900 from you earlier in the week and unfortunately it seems to be one of the small number of handsets that are suffering from random reboots", expecting to have to explain further, but the chap just said "Ah, yes, if you can bring it back we'll exchange it for a new one". No arguments or anything. Clearly they've had a few of these already.

Means I have to make another 4 hour round trip by train up to London, but at least I have my N900 - if I'd left my pre-order in place from October 25th I'd likely still be waiting.