Thanks. I just had a quick look at those threads. It'll take me a bit to digest them. Great stuff there!
For me the LT appears to be between 85% and 90% of HRmax but I'm the first to admit my training has been anything but scientific to this point. I've now decided to get more methodical about it and have much to learn.
Hopefully a more scientific and methodical approach won't take away too much of the fun in it for me.
As you can imagine I have loads of questions but I'll save them for when I've done the fundamental reading you've suggested.
Thanks a tonne.