Where can I get a large sheet of 3mm thick clear acrylic plastic?

...I want to do 'secondary glazing' on an old victorian sash window and for this I need to buy and cut a sheet of 3mm acrylic...where would be a good place to buy this? I live in East Sussex and the usual suspects would be: B%26amp;Q, Focus, Wickes erm....any other ideas or any specialist suppliers? Will they deliver, do you know? Ta.Where can I get a large sheet of 3mm thick clear acrylic plastic?
I bought some from Wickes recently. They're normally cheaper than B%26amp;Q and it is not the sort of item you can save money over the internet, unless you buy lots.Where can I get a large sheet of 3mm thick clear acrylic plastic?
your local conservatory company or you may find some in local salvage shop ( old shower door or screen should have enough clear to cut and use) and would be bought cheap
I have seen large sheets of rigid plastic covered in a peel-off film in B%26amp;Q ( in the building section)