I'd say your battery is more likely at fault. A healthy charged battery should be over 12 volts. The running voltages seem ok to me.
You're probably right. Took the battery out, using a halfords car battery charger, charged it for 6 hours. Voltage was a 12.5. Remeasured next morning, without anything even having have connected anything and it was at 12.2 again.
Phoned my VW dealer that I got the battery from last year about a warranty. Said he'll put in a request with the Skoda dealer as I have a Skoda, and it's up to them to honour the warranty (???). Despite me buying the battery from the VW parts department at the dealership
. But on a positive note he said that if Skoda doesn't honour it, he's personally ordered in a replacement battery that he can give me that will arrive Monday, a.k.a being shipped in from the UK as they don't have any on hand.