Thanks for the reply.
Yes both the ECGs were taken at the same place 2 years apart. I have been referred to the cardiac MRI by my GP now though he thought it was an over-reaction by the consulting cardiologist... expense isn't really an issue as Bupa are covering it.
I don't have any chest pains or any trouble exercising, so hopefully this MRI will put the issue to bed. Fingers crossed and thanks for the reassurance.