After all the seats went back in and the airbags were all hooked up it was safe to reconnect the battery and see if the A4 would come back to life. I’d been trickle charging the battery for around 18 hours, but wasn’t expecting much.
When I turned the ignition on, none of the airbags went off, so that was a good result! The dash lit up like a christmas tree, beeping at me once or twice, before settling down and all the warning lights going away. Sceptically turning the key that little way further the starter motor droned a few times and it was pretty obvious I was going to need the jump leads to get the engine going.
With the jump leads on and a gentle squeeze of the throttle the A4 was alive and actually sounded quite good. I left it running for 15 minutes, giving it a few extra revs once it had warmed up.
New Bosch S4 battery has been ordered from Eurocarparts.com and should show up in the next few days. Hopefully in time for the service and MOT I’m booked in for on Thursday.