I've just been talking to the elections officer.
She in the middle of putting together the new electoral register, effective from 1st December. (Have you returned your form?) In my rural district there are about 105,000 voters, she currently estimates that 10,000 people have changed their addresses or are new on the role. But currently those new details don't stand. i.e. approx 10% of the voting population in this area are affected.
If an election is called now Gordon Brown has to give 18 working days notice. Each of those 10,000 people will then need to be written to asking if they want their new details to be the ones that stand. If they do they have to write back with a deadline 11 working days before the election. (Not a lot of days there...) If someone has moved within the polling area they can still vote as if from their old address - but many may not have.
The postal votes will be complicated too. Under new rules every postal voter's signature has to be crosschecked with their application form - the computer program to do this is not finalised and where the constituency boundary crosses a district district boundary each vote will need to be hand checked. From my own experience over the past year this covers a lot of constituencies.
Sounds like a paperwork nightmare and room for quite a lot of people to lose their vote.