To be honest by avoiding all the sales talk you're screwing yourself out of a really good deal!
I know that in experience (well it worked for me with o2) when you call up and ask to move or get a PAC code they put you through to "retentions" and they offer the best deals that noone on a new contract will get.
I've heard people get ridiculous deals all just because the networks are trying to keep old customers these days, not get new ones.
The fact you want to go from vodafone to orange is a bad move too, Orange have such a bad rep recently with service (orange broadband for example!) and customer support (apparently terrible). I'd seriously call vodafone up, ask to be disconnected/for your PAC code and they'll do anything they can to keep you (free phone, increased minutes etc). It can take multiple calls, just tell them you need to think about it, they note down the offer on your file and when you call again they increase it! It worked for me, but they do ask where you've seen a better deal (basically to know what to offer/charge you in their retention deal) So it hepls to know a good contract, check out a comparison site or one of the other networks so you have a legit better offer, I used
http://www.moneysupermarket.com/MobilePhones/default.aspx and told o2 about one of the contracts with 3. Worked a charm.
Basically call them up! don't avoid the better deals they may offer, as i said I am with o2 and threatened to go to 3 and they offered me a better deal. I don't know what Vodafone are like but I can't imagine them wanting to lose your custom!
