Bad news if you're a Vodafone shareholder, they've decided they already make enough profit and don't want to take any extra money from customers. Well, it least that's my experience.

I've finally upgraded to a 3G handset - a Nokia E51 since you ask - so rang up Vodafone to add a data package to my account. £7.50/month gets me 120MB, with the first month free. Within a few days it was obvious that 120MB doesn't go very far when you're using mobile apps and emails with attachments, so I looked on their website to see what else was available. £15/month for 3GB, that's more like it, so I rang them up:

V: Sorry, that can't be added to a phone contract, it is only available with a USB modem and as a seperate contract.
Me: But I don't need a USB modem, my phone is perfectly able to act as a modem.
V: A USB modem will be quicker than your phone.
Me: No it won't. (I checked afterwards, it won't.)
V: You won't need more than 120MB on your phone.
Me: I've been using it for 6 days and I've used 80MB, I'm guessing I probably will.
V: A USB modem would be better. Why wouldn't you use a laptop?
Me: Because I don't have a laptop with me all the time.

-- we went round in circles like this for a bit --

Me: Look, I want to give Vodafone an extra £90 a year, but it seems you don't want it.
V: We haven't got a tariff that lets us add the mobile data to a phone contract.
Me: [gives up]

So there we go, they're happy to turn down £90 a year from an existing customer because their system can't handle it. If I'm going to be forced down the route of taking out a seperate 3G contract, I'm as likely to go with another provider as I am Vodafone. If I'm not able to add the 3GB to my phone contract when it comes up for renewal in July I'll be moving to T-Mobile, who offer exactly what I'm after - a reasonable data allowance that I can use as I need it.