I was an hour ago in an UK Apple store. I don't want to say the area because it will be easy to identify persons. I asked about the ECG and the girl there told me "sorry not available in EU for unkown time frame" I noticed that her name was Greek (I'm Greek)and I tried to discuss with her in Greek off the record.
She told me, I'm not allowed to say that but if you are in the UK and change the location settings to the US(of course when ecg is available in the USA) the ECG will work just fine. Nothing more needed.
This is applicable only for the gps models not the cellular
This is big news if true!