Wickes is as good a place as any of get this for a DIYer. If you don't have one near you, try phoning Jewson or one of the other large Builders' Merchants near you to compare prices. Expect discount on this sort of quantity (though not from Wickes). You will find it priced per metre and sold in various sizes from 2.4m to 4.2m in 0.3m increments. You should be able to work out which length multiples you don't want - to avoid too much offcut waste when you cut.