I have now resolved this issue and improved my sites performance by a massive amount so that it is now very very quick. I thought it might be useful for others to know what I did:

1) Truncate Event Log and Site Log (these were already very small for me but worth doing)
2) Shrink database / log files in simple recovery mode
3) Update usage stats
4) Reorganise all indexes
5) Rebuild all indexes
6) Force recompile of all Stored Procedures
7) Force recompile of all Views
8) Force recompile of all Functions
9) Clear DNN cache settings from Host settings
10) Restart DNN application from Host settings

I think the part that made the biggest difference was steps 4 to 8 as I had done the other stages before with not much difference.

It would be really good if someone would add these to a DNN scheduled task so that they could be run every so often to keep things running quickly, anyone up for the job?

Hope this might help others who have performance / timeout issues.

Nathan

Sorry I should have said, 6.1.1. Also interesting is that I have changed to use the "WITH (NOLOCK)" on some of my large tables (not DNN related) which I have a few with 60,000 to 120,000 rows but are not changed very often (one a month or less) and by doing this i have seen an increase in the general DNN speed which I accept is nothing directly to do with DNN but would seem to imply that locking is a possible issue.

Nathan