Hey guys. First of all thanks for the responses - very useful. Just to elaborate it has a slight hesitation on low speed take off at low revs and only slight throttle - if i hammer it it will pick up quickly like it usually does! And the fuel economy is ridiculous still!

I recently did a fairly big job on the car and had to remove intake/maf/fuel lines/supercharger (and more!) ... Got it back together and sorted out a vacuum leak on the intake with a new gasket.

The vacuum leak was my first thought so i tried spraying some carb cleaner around the intake gasket and no change in idle speed so i guess that's still ok.

To be honest i'm not totally sure if the reader is OBDII or not - checking that on the jag forum just awaiting a response! I plan to get a reader for it as i suppose it will pay for itself eventually! For the time being i want to get on top of this fuel problem because i don't want to be running rich and killing the cats (I'm not into animal cruelty! )

Now I have had to unplug the maf and the coolant resevoir sensor a few times recently (taking them on and off to get at things so i'll make sure the maf has a good connection and try to clean it so thanks!
*I forgot to mention that the 'low coolant' light is on and the sensor is broken, it's hanging loose below the resevoir (not leaking though and level is fine). I was assuming this would be totally unrerated to my symptoms as it only monitors the level of coolant - am i right?

Removing the o2 sensor... Hmmm i've heard this is a bit of a job sometimes do i need any special tools to do this? I have no experience with this so am i right in thinking it is on the early sections of the exhaust somewhere?