im with admiral and so far they are charging me 40 quid extra for mods - but wont replace them if they are damaged... at some point I will have to find an insurer that will actually cover the cost of the mods but not worth it yet!
As far as I understand the brake LSD cannot be disabled by turning off VDC (traction control) with the button on the dash.. it can only be disabled by altering some wiring. Brake LSD is not a "mechanical" LSD but works in parallel with it - to be more correct the LSD in a 350Z isn't mechanical but viscous.
you may be able to go on a "speed awareness" course in lieu of the 3 points - depends on the juristication of where you were caught and so on.. wouldnt save you money as you have to pay for the course..
eg for Norfolk.. http://norfolk-safety-camera.org.uk/ind ... speedaware
if you get the 3 points remember to declare them to your insurance - 3 points wont (shouldnt) make much difference to your premium.
I know they CAN take your plate off you - the DVLA can cancel it.. not sure of the details of it though.. would certainly suck, you wouldnt get any compensation (which would be annoying if you had an expensive plate!)