Ok, attempted to make the contact point higher this morning. Some improvement I think, take a look at the video if you get a chance (two serves this time, second one is probably better.)
Re slowing down the tossing arm, I've been trying to do that but don't feel I can get the power into the throw if I make the action slower, though I need to experiment more.
Still not pronating late enough I don't think, you can see the racquet face when it's behind my back but it flattens out a bit too soon. One reason for this is grip, I tend towards a grip in between a continental and an eastern forehand for the serve. Was trying the full continental for a while but it seems a bit uncomfortable, I think I need to isolate that aspect and practice it more, unless I can get away with a semi-continental grip, not sure.
Finally I don't really feel like I am uncoiling with enough force at the moment, still concentrating on timing the contact point and getting the knee bend right etc, not able to 'explode' up at the ball much really. Hopefully I can move onto this aspect when I have the other elements more locked down.
Pleased with progress so far anyway, thanks for all the tips in this thread. Not much chance of me getting discouraged I don't think, you get out what you put in, take small steps towards the goal, and so on, and on.