Found this link http://ctyres.co.uk/ cheapest tyres that I've found and they deliver too.

cant seem to find any 13's on the site??? do they not sell any?

I use blackcircles.com they fit them included in the price, just checked and there the same price as this but with the fittment.

mytyres.co.uk are good too.

Paid less than £20.00 plus VAT for my Yokohamas, 195/50/15 fitted and balanced . I used to be the manager of a small tyre company and paid cost price