Thanks again, all sorted now. I'm off to Glasgow in the morning to collect!
Just to clarify for the possible future benefit of anyone else in a similar position;
You can tax online with a new style MOT and the V5 reg. document as well as valid insurance. However, the database that is used to check the insurance is only updated periodically so, in my case, it wasn't possible to buy the tax in time as the insurance was only purchased late Fri night.
Other options are to go to DVLA office or Post Office but you WILL need an original insurance policy document. Again, in my case, this would not have been possible til Mon or Tues when it arrived via Royal Mail.
What I have done is insure my car with a company locally to me that also has offices in Cumbernauld where the car is. The seller has kindly picked up my insurance and gone and taxed the vehicle for me all in the nick of time!
So, I'm deciding whether to fly or National Express up to Glasgow now. Not much in it price wise but air taxes bumpt things up a bit so am deliberating. Am tres excited.
It's an oldy car I'm getting but I'll be able to fit car seats in without grazing my knuckles as is much bigger than my little Peugeot which I waved a slightly sad goodbye to yesterday.
Ahh, are you all asleep yet?