I'd agree about the birch ply as one of the better buys at the moment
for furniture. It tends to be very flat and square with a very uniform
structure and attractive outer faces.

Like all sheet materials 8 by 4 feet (2.4 by 1.2m) is the standard
sheet size, with other sizes derived from halving that. 18mm thickness
is the most commonly used.

Ask specifically for birch ply or if they don't have it, red ply. I
think I got mine from Travis Perkins last time.

Some useful info he http://wiki.diyfaq.org.uk/index.php?...heet_Materials