Thanks for the replies.
The dealer has suggested that we can just get the tyre fitter to slit the valve to let the air out, keep it and then detach the sensor when they send us a replacement tool.
Are the tyre pressure sensors useless? Currently all 4 are red. The tyres are not visibly under inflated - not a good way to check but the best I can do for now. I thought there was some kind of remote sensor in the car that indicated that they were under inflated so I did not realise what the red caps meant when I picked the car up on Saturday. I thought they were always red.
Borrowing a tool to remove all the sensors may be handy if the tool from the dealer does not turn up in the next few days - I would not want to end up stuck with a flat tyre somewhere and not be able to fix it. If the tool does not turn up soon I will probably be begging to borrow one from a local saviour in the next few days. I live in Ash Vale and work in Fleet.
I'll have a quick go with some pliers gently in the morning.
We are not having much luck with cars at the moment. My wifes company car is waiting to be picked up for repair after she was hit gently by a taxi and the courtesy car has not turned up.