Thankyou for the replies, they are helpful. I have been reading a lot about the subject, it's quite interesting.
I've noticed that my mood has changed a bit, and wonder if it is possible to have a " come down " after about four hours when the effects are wearing off. I can get a bit short tempered and have been outspoken also, moreso than usual. Not that having attitude is a bad thing!

My heart beating fast does not seem to be a problem. I was worried because I have a naturally very slow heart. My Dad does also and he'd always believed that this was a healthy sign until he discovered it was otherwise and has a pacemaker now. So I should be cautious.
Thanks again!