Cheapest suppliers of Alu?

Ah yep, should have given a bit more detail. Indeed I did order a couple of quite long lengths (1480mm) in the 25mm. Didn't check on small quantities so things could look very different. Also the grade was regular 6082T6 vs. 6061 from alu warehouse. Not exactly like for like either then but its great that there's two fairly decent suppliers of alu to pick and choose from.

Ps. Not going for a full alu bed but rather a hybrid alu/ply after the suggestions on here. The alu is primarily firm up the long unsupported extrusion with the X profile rails on.