Having changed two tyres last year it was time to do the other two this year as they were 7 years old. Although there were no signs of degradation the age was against them. I did a fair bit of research last time and found Selecta Tyre in Newark to be the most cost effective at £39.85 all in inc VAT each. When I phoned them this time they had the same make for exactly the same price and in stock, so the deal was done and they are now fitted.
A few points to note.
Always make sure you are replacing tyres with the correct load rating for your caravan, it's not sufficient to replace like for like as the ones fitted may not be correct.
Check the Max Laden Weight or MTPM (max technical permitted mass) and divide into that the No of wheels on your caravan.
For my unit the MTPM = 1750 kgs / 4 = 435.7 kgs. So I went with tyres of load rating of 475 kgs being a "T" rating.
Always go with the correct pressure, check with the specialist who will be able to give you up to date information on this.
Lastly when re-fitting the wheels remember to torque up to the correct value and in the correct sequence.
The torque should be re checked again after 50 kilometres or so.