...I have just replaced the tyres on our Sterling Europa, although they looked and seemed ok, £130 is ok for piece of mind! I too take my wheels off and take to the tyre fitter. I ordered them from Camskill - I purchased Hankook Vantra something or other (obviously the correct load rating and the rest), went to storage, attached the van to the car, jacked up one side and replcaed with the spare wheel (took the opportunity to lubricate all the relevant parts on the spare wheel carrier), lowered, jacked opposite side and replace with a winder wheel. My tyre fitter is also a good friend and keen caravanner, so is 'appreciative' so to speak!
Would be worth checking with the tyre fitter that he can deal with Tyron bands if you have them, and I had mine balanced etc too.
If you get the van done on your drive, you might need to have the chassis manual handy as a point of reference for the fitter so he can double check the lifting points, OR, as its a twin axle - my mother in law has a T/A horsebox, and carries something that she calls a 'trailer-saver' essentially, when she got a flat a while ago, with horse onboard, all she does is pull the trailer up onto a ramp like device (looks like a leveling ramp) to unload the flat tyre, thus enabling the change without jacking - is this possible for a caravan?
Cheers
Rob