Large Format Printing Help

[gandalf]

Am looking for help to get two A4 PDF documents blown up as large as possible ideally to around A3/2 size and onto some sort of board for display purposes for the forthcoming Big Bad Wedge Festival (15.06.06)
As we have no budget for this event I am rather restricted on how much I can spend so any help on the pricing would be much appreciated - if anyone can help or point me in the direction of someone who can I would be grateful.
PS one poster is b/w only the other needs to be 3 colour (only simple text and line drawings) no 4 colour seperation or Tiff/jpegs involved.