I have recently bought a
Jobu Jr Gimbal with an optional horizontal mount. Without the horizontal mount it is a sidekick and by fixing the horizontal mount it becomes a full Gimbal. Superbly made piece of kit and only weighs 0.63 KG. The Jobu Jr comes in at £149 exc the optional horizontal mount (just noticed it has gone up to £179).
I did try a friends Indian knock-off Gimbal but for my lightweight set-up (400/5.6 + 1.4tc) it was an overkill. I find the Sidekick much better at tracking birds than a ballhead.