UK stockist http://www.netmerchants.co.uk/product.php/9431/0/medieval_castle (£27.95 plus £6.75 P&P free postage to UK over £45 ex VAT)
Wow that castle is brilliant, i love it.

On this site i've also seen a trebuchet
http://www.netmerchants.co.uk/product.php/2265/859/trebuchet this is also 1/72 scale. My friend needs a few for his bretonnian army.
But i've looked up that scale and it says that's for 25mm models. Is that correct?
Should i be looking for 1/161 scale?
Here's what i think are the correct scales....
54mm = 1:32 scale
45mm = 1:35 scale
28mm = 1:64 scale
25mm = 1:72 scale
20mm = 1:76 scale
15mm = 1:100 scale
12mm = 1:144 scale
10mm = 1:161 scale
6mm = 1:300 scale
"O" (1:48), "HO" (1:87), and "N" (1:160) scale are popular among model railroad hobbyists.