In message , Andy Hall writes
I believe the CLS started being imported a few years ago only in some weird "standard" sizes, 63x38mm ISTR (2.5"x1.5"). Local yard only stocked in 2.4m lengths. Then all the 2x3, 2x4 etc carcassing timber went to the "regularised" standard, which amounts to the same as CLS, i.e. planed and round corners for safer handling. Still nominal 2x3, 2x4* etc, but actually a tad smaller due to the planing. Certainly available in long lengths to at least 3.6m in a good yard. Although round here its not treated as Andy mentions above. The C16 treated is still square and sawn finish. YMMV.
(*OK, 75x47, 100x47)