Thanks Folks, I've had a trip to my local dealer and I'm investing in a Manfrotto 058 Triaut Tripod LINK
http://www.manfrotto.com/Jahia/site/...lsf=68&child=1
with an Acratech GV2 gimbal ballhead LINK
http://acratech.net/product.php?productid=9
I think it should do the job - I also have the 500mm f4 P Nikkor.