Cheers guys, 2mm & 3mm is exactly what i'm looking for too and seems to be that even local suppliers cant do this grade at these thicknesses. One option is machining down from 4mm 6082 plate, but this is going to end up costing way too much for the quantity/sizes required.

I may have to just test my luck with the 5251, but got a feeling that roughing it out with a 3 flute rougher tool (as normally done with plate) isn't going to go down too well...