Thank you both for your replies. In the end I have had to order another remote from Germany but there is a 7 to 10 day wait and the cost is likely to be £60. On a positive note, however, I opened up the old remote and found that the switch mechanism had become detached. I have resoldered the connections and this has meant that I have been able to switch the alarm off and hence use the car. I am not confident that the reconnection will be durable and so will be not using the alarm unitil the new remote arrives. I will then use the old remote as a back up. The lesson for me is that the PCB inside the remote looks extremely durable and so errors are much more likely to be due to a faulty connection between the swith mechanism and the PCB. So for others in a similar position I would recommend that they try to DIY the remote before discarding it.
Once again thanks for those that took the time to reply.