From the original poster, Quintin Lake, we have the following statement/question.
Therefore I'm guessing my series 2 gitzo ( GT2541 with RRS BH-40) isn't sturdy enough or perhaps there are are other long lens techniques I'm getting wrong???
At the end of page 2, we have the answer from Ben Rubinstein.
Neither the tripod nor the head were designed for that kind of focal length. I have a 2542 and the BH-40 and would not begin to use them for lenses over 300mm and their manufacturers do not recommend over 200mm. Add long exposures to that and you're just asking for trouble I'm afraid.
The problem is solved, and as is often the case with many problems, the simplest solution can be the best. Buy a sturdier tripod.