Hi Andrew,
I didn't upgrade the Kernel - I don't use Thunderbolt, so it hasn't come up. The Wifi worked without me having to do anything. I did look at changing to the fully open source driver, but as it didn't make a difference I didn't include it here.
As for 14.04 - I did it in the (possibly mistaken) beleif that it would be unlikely to receive an update that breaks everything. As this is my work machine, I'm happy to stay on a stable version rather than bleeding edge.