Severn Ply have a reasonable range (26mm veneered) including Ash veneered both sides A/B, which I assume means one is better than the other. See here http://www.severnply.com/products/vb03.php
You may be interested in my post earlier in the projects section which refers to their cutting service - it wasn't very expensive as I recall and I really didn't fancy heaving all those sheets of 25mm mdf around.
Thanks for all the replies, I have found this, http://www.lawcris.co.uk/product_detail ... roduct=600 they are more local to me than the other suppliers you have mentioned
But this is to be used for church furniture and it seems to be C grade verneer both sides, i dont think this will be good enough for what i want