How does servo Jitter manifest itself?
I have a servo with a choke. The servo works fine apart from if I release the steering from the end point, the servo centres but then jitters slightly around the centre point for about half a second.
Any Ideas?

possibly interference from power wires onto the signal wires? try separarting power and signal as best you can.

What you need is a power cap thingy for your reciever:

http://www.apexmodels.com/gbu0-prodshow/SPM1600.html

Along with protecting the servo, it also stores power for the servo cutting out interference.

had one, in an attempt to combat morcambe random left turn on the straight made naff all difference just got in the way

You could have you aerial in contact with something carbon.