As above I need some rear tyres prior to Donny on Sunday, where is the cheapest place?
Camskill 
Deamon tweeks have (had) these on sale Ade… about the same price as Camskill… next day deliver too!
I believe BAT also carry a van full so you may be able to get them changed there. 
Found some in the end on eBay Linky cheaper than camskill and next day delivery 