Just a follow up to this... I wish to retract based on a conversation with O2 CS... very helpful this time around:
Chris: Hi there. My name's Chris I am an O2 advisor, may I take your name please?
You: Hi Chris, I'm Philip.
Chris: Welcome to O2. What brings you here today?
You: I'm interested in simplicity for the iPhone.
You: I was thinking of getting a 1 month simplicity plan. This includes unlimited data and wi-fi, correct?
Chris: Yes you get unlimited access to the internet and wi-fi as well.
Chris: How does that sound?
You: Sounds great. I understand though O2 will be introducing a 'cap' on this free internet in October. If I sign up to a simplicity plan today, will I still have unlimited data and wi-fi after October?
Chris: If you sign up today you will keep that unlimited allowance on your contract until you decide to cancel it.
Chris: That way you can be guaranteed to beat the cap
You: So to confirm, even though it is a 30-day rolling contract, I will get unlimited data/internet regardless of what happens in October?
Chris: That is correct.
You: That's excellent news. And if I got this today, could I use it with the new iPhone 4 launching next week?
Chris: Yes if you want to use it in your new iPhone you can just exchange the sim for a micro sim and we will keep you on that tariff.
Looks like I'll be sticking with O2 on Simplicity!