Cheap worn 36" tyre

I am looking for a cheap 36" tyre. I do not mind how worn it is as it is for a 36" ultimate wheel that I am building. I live near High Wycombe in Buckinghamshire, so a UK seller would be preferable to reduce postage costs, or I could collect if the seller is not too far away.
The cheapest tyre I can find is £60 new from Unicycle.com which is rather expensive given an entire new 28" ultimate wheel is £94.