I love OperaMini - works great for Mumsnet whereas the built in browser is really slow at viewing Mumsnet. Glad you like it Sandy
Not sure which providers are still doing capped internet usage in terms of how they market the service to customers. Having had a quick look around appears that major providers are doing Unlimited web for a monthly fee but if you read the terms carefully you will see a Fair Usage limit mentioned.
Think the 1Gb, 3Gb thing I mentioned before was for Mobile Internet (which is where you connect your laptop to your mobile).
3 seem to still be doing a Free amount of data with each TopUp, then a charge per Mb of data - see 3Pay. They then have an Internet Add-on which adds unlimited internet for a fixed duration (such as a day or a month).
TescoMobile do a 7-day (GPRS data) internet pass for £2 per week (auto-renews) on PAYG. 100mb limit is mentioned but not clear if that is per day, per week or per month. On their Pay Monthly Sim Only tariff they say it's Unlimited data but fair usage limit is 500Mb per month.
ZsadistsShellan - consider if you want to stay as PAYG or change to Pay Monthly. Then look at the various tariffs on offer by your preferred network.
I view myself as being a fairly heavy internet user on my mobile. I use it for Twitter, Mumsnet, Email and occasional YouTube Videos. Last month, I used 96.96Mb of data. Previous month to that I used 54.8Mb, before that 81Mb, before that 92.65Mb. So while Unlimited packages do have Fair Usage limits, you may find that you are well within that limit.
Remember that it is Video and Audio that will use up most data - so use those with care.