Hi Martyn
It may be possible for you to use some of your PGCE credits as credit transfer if they are less than 16 years old. For information on credit transfer and how to apply please see the link below:
http://www.open.ac.uk/study/credit-transfer/
Depending on which modules you choose you may be able to start this course in February. The final date for applying for credit transfer for a February start is 10th December. Information on the Open Masters can be found by using the link below:
http://www.open.ac.uk/postgraduate/qualifications/f81