ECG
A colleague renewed his Class 1 in the UK prior to coming to CX for an interview. No problems. The CX ECG spat out a problem. "t rhythm anomaly' or something. He had to have another ECG back in the UK with a cardiologist. Cost him £450. The specialist said there was nothing wrong with either the CX print out or the one just done. He was embarrassed to take the money.
Speaking to the Docs here it's commonplace. You don't need the medical, unless you have other reasons to renew, as you must have one here.
I wouldn't lose sleep, especially as you said no cardiologist was present. It's probably just the machine.