Hi Charley 2006, I completely agree with butterfly0000000 and completely disagree with Selmer. Although PFOs are common, people need to be very aware of the fact that on occasion they can lead to serious symptoms, complications and even death from fatal strokes or heart failure.
Thank goodness you live in the UK where you don't have to worry about insurance issues like we do here in the US. And I had the opposite experience. Doctors at first ignored my symptoms because I was 38-39 at the time I started developing symptoms and in great physical condition; all my basic tests (BP, iron, cholesterol, stress test, etc.) came back perfect but I kept persisting because I felt awful (short of breath and extremely tired all the time after being very physically active all my life). I was the one who asked for and demanded additional tests, and I have incredible insurance coverage here in the US. After more intensive tests they finally discovered by PFO and I had the closure 6 months ago and I am feeling almost back to normal.
So, my advice to you is that if doctors suspect something MAY be wrong, have it checked out. It could be nothing and at least you'll have peace of mind. Or, it could be something and thank goodness you had it checked out and taken care of before it become something more serious developed, don't you think?