
I got that offer :) I've been shopping around for the best deals right now anyway so I'd caution you on two things with it. One, I'm on option 3 but only pay 20 a month so it would be an extra £10 for me. Check which option you have and how much you pay - it might be less than the standard 25 they list in which case it would cost more than 5 extra. Second, and this was the big one for me, I'm not sure that offer includes GPRS for internet access. The way I read the (very small amount!) of information given you had to either be at home or near a WiFi hotspot to get internet access. The phone itself looks like it has GPRS if I found the right
model but GPRS access isn't listed in the offer. I'd check with the person on the phone whether this is true or not. I doubt many venues for shows will have WiFi hotspots within range so that would defeat the purporse for you. Having said that if you do already pay 25 for an extra fiver it's kind of a nice phone.
As for monitoring usage there are apps you can get for free. I use GPRS monitor on my PDA/phone. You can input how much your fee usage is and the software will warn you if you go over and by how much so you don't get any nasty surprises. As for how mucy you need it depends on how graphic rich the sites you visit are or if you get attachments in your messages but I'll give you an example. I wanted to do some price comparisons in Costco so looked up how much a mixer was at Argos. That used about 400Kb. A plain text email message with one or two paragraphs is about 7-10Kb.