Don't wait, get there early with a deck chair and sleeping bag.
When I bought my latest car it was very close to the end of a month. I could either wait 6 days, without getting in the thing and Tax the car at the start of the new month or tax it now and pay 1 months tax for the last 6 days of the month.
When you work it out, a years tax costs about 50p a day. Just about £2 a day so I could drive for the week. Worth every penny.
Oh yeah, welcome along!