I hadn't realised that lots of people were in the same situation as me. Still, at least the Pioneer rep I spoke to said that the upgrade had been released in the UK a few days ago and should be orderable from suppliers.
Pioneer support just said it might cost as much as £150!
They said it had been released a few days ago and that there was plenty of stock so that somewhere like Halfords would be able to order it in for me. I really hope that internet retailers are going to charge less than that.
I've been trying to find someone who actually sells this, as I don't have the time to not simply be able to drop in the newer 3.00x firmware updates as they are released by Pioneer.
Has anyone found a place selling this in the UK? Thanks.