Looking again at the baptisms I worked backwards from 1747 and think you are right that it was 1742.
I have looked again through Cheldon and Coldridge for marriage but without success. I have also looked outside of Devon but no luck. Coldridge is about 12.2.km (20 miles) from Cheldon by today's standard.
Perhaps they weren't married. Mammoth task to go through all local parish records. Sorry could not be of any more help. Sally