Just a bit of a rant......with a good outcome
Went to Glasgow dvla office to change the v5 taxation class only to find that it had closed down in Dec 13. So that was a day wasted for me.
Popped into my local post office, told her my sob story and asked for advice and she said no problem we can do that for you. So the v5 was sent away and I got my new tax disc.
So it actually can be done at a PO. Don't know if this is only due to all the closures but saved me sending everything to dvla and waiting weeks..