Just been to my local 'the works' ( that discount book shop) and they've got packs of a3 foamboard in. 5mm thick for £2.99 for two sheets, which is cheaper than my usual source. of course they only have as much stock as they have, get em while they're hot.

I go to my local plastics place (Mulford Plastics for you Aussies out there).
They have 5mm foamboard for around $15 for an 8'x4' sheet. Much cheaper than any art or craft shop.

Holy crap, that's amazing! Thanks for the info.

_________________
'Viv'

Broadcasting at http://www.youtube.com/rubbishinrubbishout
Laying down dice at the Battle Bunker Gaming Club http://www.battlebunker.com/forums.php

The tradeoff is that the local place DON'T have high-impact polystyrene sheet (other outlets do).
They also have 3mm foamed pvc sheeting that ranges from $25-50 an 8'x4' sheet (white is cheapest, Black is most expensive).