Thank you all for your advice. I went to my GP this week and he agreed with me that I should not, at this stage, be working. He did say that over time it is something to work towards but for now it is a bad idea. I wanted him to sign a form to say that I could go swimming to help loose weight and he even wouldn't do that, he said to ask my cardiologist when I see him this next week (lots of days out at the surgeries, yeah!)
He did say that he would be more than happy to provide me with a letter to support my case though, so that is good, and he seems a lovely doctor as it was my first time of seeing him since I moved practice due to house move.
I did have a really bad day on Tuesday, my heart was jumping all over the place with the beats and I was very close to calling an ambulance but I rested and over time of a day and a half it calmed back down. It might have had something to do with the doc prescribing me with a new inhaler and the steroids in it might have disturbed the ticker a bit. 