OK, well I have spoken to Dell Tech Support, who suggest that it needs a new motherboard for which they want to relieve me of £366
In my view that makes it very marginal to repair.
On looking through ebay however, I found
Dell XPS M1330 nVidia & Intel Graphics Repair Service on eBay (end time 28-Sep-10 16:24:01 BST), which looks like taking a punt on.
Does anyone have any feedback or thoughts?