Well I got hold of the 'final' RTM build and had a right TaTa installing it!
Install from within Vista took 20 minutes or so, then my PC rebooted and loaded to a 'Configuring updates Stage 3 of 3' screen and rebooted again after a few seconds? Loaded to the same screen and spent the next hour and a half accessing the HD for 30 seconds then pausing for 15 minutes and repeating.
Reset the PC and it went past the Stage 3 of 3 bit and went onto installing Service Pace 1 Stage x of 3, it did all that then went to a black screen with a mouse pointer and did the same 'HD access and pause' as before. Reset the PC again and finally Vista booted but said 'True Vector' had drivers incompatible with SP1 and wouldn't let me get on the net! True Vector is part of ZoneAlarm so had to uninstall and reboot for SP1 to finally work!
Conclusion: UNINSTALL ZONEALARM BEFORE INSTALLING SP1!!!
I think this was the cause of SP1 'pausing' due to ZoneAlarm drivers.
Fortunately the 7.1.247.000 BETA build of ZA for Vista is compatible with SP1: http://download.zonealarm.com/bin/free/beta/index.html
SP1 is now installed and Vista still activated, no 'expiry' messages! Tried Windows Update and that worked as well. The only problem I have with WU is it shows 6 driver updates for my nforce board and a raid card that all fail to install, this happened before SP1 too! A little googling of the error message 80070103 suggests the drivers it offers are not the best for my PC and fails to install them! So why keep offering me them if it won't install them?