I finally got the go ahead from my client to update there wordpress website and all plugins.
Updated WordPress from 2.9.2 to 3.5.2. It has gone really well - all plugins updated and working. Really went well.
However, not really sure the best way to upgrade from 'Atahualpa 3.4.5' to the latest? Is an incramental upgrade better? Maybe get to 3.6 manually and then export? Or is better to just upgrade automatically to 3.7?
I have a lot of customisation in place that I do not want to lose. Database and Files already backed up.