Would be a good idea for everyone having these problems to contact HTC on 01279 206906 (thanks to "Say no to 0870" for the landline number!), so that they can see the software update has caused a widespread problem.
I spoke to Luke in Technical Support, and had my call escalated to Daniel in the Customer Care team - try to speak to one of these as they should both know about these issues as I asked for it to be fully documented.
As for me, I have finally had to admit defeat and have given up with HTC (I have had 4 faulty handsets since upgrading my contract in July), I need reliabilty for work purposes, so have gone back to Blackberry.
Wish you all the best of luck with sorting this issue - please keep this post updated.
Oh - I have a spare brand new HTC desire S battery if anyone wants it ?