The keyfob battery on my 2007 Ceed is going so I checked out here which has been very useful, so thanks. To double check the battery type, I opened the case, first leaving a drop of WD40 on the screw, then opened carefully. I took out the old battery, a CR1620, and refitted as have no spare at the moment. Then I tried it back on the car tomake sure that removing a battery didn't upset the eletronics, and all worked fine.
I have now ordered a new Duracell CR1620 from Amazon at £0.95, so when that arrives will change out the old one and expect all to be good again. Will report back.