It seems to be accepted by all that you always need more clamps. If you can get some and not break them, they will always have a use for them, even if you get better ones later that are your first choice for most jobs.
Unfortunately if you need 4 clamps, you can't get away with telling the glueup, "ah but I bought 2 Besseys instead".
With that said, I won't buy them from Rutland's. I am lucky in that I have a few clamps already so am adding to my collection rather than starting it. I also have some long clamps, and am lucky that 300-600mm ones are cheaper than 1200mm+