Like the old adage of a plumbers leaking tap never gets fixed, I had been running my own server to host all my email and try to keep all the various devices and access methods in sync, and should have really moved to a cloud based solution far sooner than I had.
So, with a spare day I took the plunge and after weighing up the differences between Office 365 (from Microsoft) and Google Apps, given that I'm still very much an Outlook kinda guy Office 365 just managed to pip Google to the post - and I'm happy to admit, some of Microsoft's products are brilliant, Visual Studio and SQL Server Management being a couple of the jewels for me. That said, I do think the Google Apps offering is probably a better rounded solution, and if you do not use Outlook then I would seriously consider it. Once down to the actual task at and having done many migrations of data, email and systems for corporates, the basic nuts and bolts was pretty easy, and getting a seamless transition of emails flowing the right way was simple.
My problem laid in my archives! With 25GB I thought I'd put a couple of my old archives on there as well, however from some time back one of the PST's had 3 copies of every message, not good.
Searching around for a duplicate remover, I found this: http://www.vaita.com/ODIR.asp - Not only does it work very well for email messages (checks the email message ID so will only get genuine duplicates), it's free! While the interface does look a little basic, this is a genuine case of function over form, as it has everything you need, and just works. The fact it still works on Outlook 2010 shows what a robust little tool this is.
So, thank you VAitA, for publishing a splendid little addin for us all.