[Stuart]

A January election IMO is a no go simply because no one wants to campaign over Christmas and it would lead to a very annoyed electorate and equally annoyed MPs.

These days, I think most of the campaigning people take notice of is done through the media, so the time of year is irrelevant. Random people may stick leaflets through my door, but they go straight in the green bin. I also don't answer my front door to anyone unless I'm expecting them.

Most of the campaigning would be in January if they decided to run it down to the wire. Frankly, if you're an MP (of whatever flavour) with a seat on the gravy train, you're in no great hurry to bring your ride to a premature end.

28 January (a Tuesday) is the last possible date. There is no stipulation that GEs have to be on a Thursday, although they always have been since 1931. The reasoning was that the great unwashed got paid on Fridays, so would be too drunk to vote. They would be penniless and sober on Thursdays.

If they went for Thursday 23 January, that's still plenty of time for campaigning after New Year. I think people generally get tired of blanket coverage after a few weeks anyway. People still go to work in the middle of Winter, so nothing to stop them voting on the way home.