[Marwan]

Looks like youre on the right track... i would say get the Cayman HF... I dont think there will be much difference in performance, but probably the Cayman will be a more comfortable gun to use with its newly designed Grip and better balancing due to the design of the barrel. This will have a positive impact on accuracy ofcourse, but i dont think the difference will be notable...
Not sure where you will find rob allens in the UK, but dave (spearo.co.uk) sells Rabitechs that are very similar to Rob allen