So I think I've found a solution that although not ideal works for me.

Firstt I downloaded a trial version of SyncMyCal from here installed onto my WinXp box (with Outlook 2007 installed), then installed GPEcalendar and Erminig on my N800.

Setup SyncMyCal to sync with Google calendar on the WinXP box, then setup Erminig to sync Google Calendar with GPEcalendar on the N800 and hey presto!

Bit of a roundabout solution but it seems to be working just fine for me. However it's not clear what the terms are for the trial version of SyncMyCal so it might just expire in 30 days or something. But at $25 it's not gonna break the bank to get a full license. To be honest though I would have much preffered for Nokia to get on top of this rather than having to pay for a third party service.

Anyways there it is, hope someone finds it useful!