You are correct walkinTAS, the 'Subscription' feature only sends you an email the first time something new is posted in that thread.
Anyway, thanks for listening and actually acting on it so quickly

I only have two little niggles with the new set-up.
One is I find the words 'Subscribe' and 'Bookmark' a bit ambiguous/confusing. On nearly every other forum I follow the 'Subscription' feature is the same as 'Bookmarks' here. Others use a phrase such as 'Follow thread', which I think is more clear. Perhaps you could reconsider the terms, or even amalgamate the two features? By that I mean have one page for your the threads you wish yo follow, from where you could elect to receive email notifications or not for each thread/sub-forum. I am not sure if the platform would allow it but you never know.
The second niggle is a very small one. Personally I like it when there is a little kind of breadcrumbs beneath each thread on your bookmarks page. All it would have to say is the sub-forum that the thread is in. This is handy because it allows you to easily identify which sub-forum a thread is in, as well as providing an accessible link straight to the sub-froum. This makes checking the site so much easier as you can easily browse sections of the site all from one web-page (bookmark).
They are my pre-coffe musings so forgive the ramble.