Thanks to everyone who expressed concern after my post the other day about my heart.
I saw the GP today & she told me there are a number of minor problems - a mix of leaky valves & enlarged bits. It's nothing immediately to worry about but more tests to be done & a possible cardiologist referral. Interestingly though, she did say that some of the trouble is probably connected to my long-term lung problems. The low heart-rate is a separate issue that she will test as well.
Anyway, I'm a bit stressed trying to see what Dr. Google makes of it all, but I think fortunately there are no major immediate issues.