The best way to contact me is by email, at one of the addresses provided on this page. I ordinarily check email every day.
I generally have my mobile with me, and switched on. If you call and can't get through, it generally means that I've run out of battery power, am on the phone to someone else, or have deliberately disabled incoming calls for some reason. I don't at all mind being called very late at night, especially if it's international - if I didn't want to receive calls I'd have the phone switched off.
The phone number is: 07779 296469; callers outside the UK want to try +44 7779 296469.
My home postal address (for the time being) is Cobbers, Conduit Head Rd, Cambridge CB3 0EY, United Kingdom.
People occasionally have cause to send me encrypted email, particularly for sensitive passwords. Several PGP keys with my name on them are in circulation on the Internet keyservers. The one you want is 0x4E02E32F, though the email address associated with it it is now no longer in use.