Once booted up and logged in the PC does run a lot better now, programs are not freezing as they were. The only things I seem to be stuck with now are on boot up.
The initial boot up to the users screen is pretty quick, once a user account is selected it takes a full 3 minutes for the AVG firewall to become active and 5 - 6 minutes before the PC is usable. I have been into the AVG settings and de-selected all the run at startup if task not completed options thinking this may be the issue but it makes no difference.
Checking the running processes in task manager reveals 2 AVG programs using up to 100% CPU, these are (AVGCSRV.EXE and AVGWDSVC.EXE)
The only lock up I seem to get now is changing between users. Where the icons or taskbar do not come up. The task manager shows the account active but there is nothing on screen.
Overall the PC is far better than it was, I think fixing some of the issues has just highlighted where the main problem lies (AVG)you probably wish you hadn't offered to help me now as I seem to be moving the goalposts as time goes on.
Once again thanks for your continued help