not hardwood - but I like reclaimed pine - say at least 1 inch think

fo a supplier try http://www.traditionaltimber.co.uk - mind you I do not expect you require very much - so perhaps a this company will not be practical for you.

also at 1200 mm wide - you may need to have some mid-support

good article here:

http://www.diyfixit.co.uk/nflash/bui...g/shelving.htm