Quack with an interest in Cardiology here.
Glad to hear it is electrics rather than plumbing. Much much better. But this is why I said you should get on and phone 999. It is good you were still in AF when they did the ECG at the surgery. Sometimes it can take a while to hunt this down properly and I am not surprised you had the angio done. Effectively you were getting a form of angina – but luckily because of the way the AF limited your coronary artery function rather than because of blocked arteries.
DC cardioversion is really nothing more than a reboot. Your heart restarts after a tiny pause. Totally routine. It isn’t a drama like people getting zapped in “Casualty”.
AF does just happen quite often, but can happen as a side effect of a chest infection. But some people do get it coming and going in which case we now have good drugs to keep it in rhythm, and techniques like RF ablation can be very successful.
You need to be on the Warfarin for 3-4 weeks before DC shock, except in emergencies or where you can prove the AF came on in the last 48 hours and for 4 weeks afterwards – and warfarin will probably be the biggest nuisance element. I have a couple of very active friends who have been through this and more who are still riding/running.
You’ll be fine.