Hi there
Just read Stu's posting and thought I would post here for everyone to read and try... Stress and worry about the ectopics definitely makes mine worse.
My CBT therapist has given me an interesting exercise to try... if you focus on the weird beats you are subconsiously (and often consiously worrying about them). So the idea is and this may seem a little simplistic, is to sit somewhere quiet, close your eyes and focus consciously on the weird beats, say to them that you know they are there, and that you know that they won't harm you. (You might not believe this at first, but try to say it with conviction.) Then move your focus to the rest of your body calmly and focus attention on for example your kneecaps or your earlobes until you can find a harmless sensation there, then give it some attention, then move elsewhere. You will discover that any time you focus on your body you can find funny feelings. These are fine and harmless and happen all the time apparently. But it is the focusing on an interesting symptom that your brain latches on to that increases the anxiety, and will prolong the discomfort of a funny heart beat.  It is a form of mindful meditation. Try it for five minutes. And if it works you can increase the time if you like doing it.
I have tried this last night, I have tried to focus on tingling in my toes that I know is normal whenever my heart is going really odd on me, and so far it is working a little. It needs practice.
(You're probably all going to think I am mad now!)

I have heard that the 'mindfulness' thing can be helpful for anxiety and stress. I can't remember if someone else posted this explanatory link previously, but I found it interesting as I didn't really know what mindfulness was:

http://en.wikipedia.org/wiki/Mindfulness