Hi Tara,
Just a suggestion, as I've not really thought it through (early on a Sunday morning
). But if you were to buy a cheap private plate from the DVLA then you would probably save yourself the hassle of being pulled over, and being messed about at the petrol pump.
Also it would be instantly obvious to the police or anyone else that see's your old number plate that they are possibly the little gits who are trying to get away with something.
I know it will mean you have to spend a little money, (which you shouldn't have to!) But it might save you some hassle