Do you know anywhere online were I could get these printed up at good quality but low prices?
Just done a quick google for you and http://pixel2print.co.uk/products/posters came up pretty cheap 50 for £9.99 A4 sized.
You should check it out. Otherwise local stationery shops often offer printing services for low costs.
Hope that helps,
I think JD has found you the cheapest supplier going there if you want professionally done posters, so kudos to him
Of course, if you just want a few to hang in shop windows etc, your local library will do printing. It's a basic option, but you should be able get them for about 20p each.
Hope that helps