My car came with cheap ebay metal dust caps that now dont want to come off

Im tempted to get the pliers out but i dont want to damage the valve itself

Any advice before i visit the tyre repair "specialists"?

Pliers should get them off but don't crush them. If your using metal caps smear the threads with grease to prevent it happening again. 

Will try tomorrow thanks

We had this on my sons car, after fubaring a valve using pliers we went to our local tyre depot and they just poured boiling water from the kettle on them. It sorted the problem.

spray from back in to it with penetrating oil leave over night

The hot water usually works. If all else fails, take a junior hacksaw to the caps, cutting at an angle through one side taking care not to go through to the thread on the valve. Once you have a decent slot, twist a screwdriver into the cap. This should split the cap enabling removal.