It's always irritated me that UK (and many other) operators have missed the opportunity to offer data-only tariffs aimed at handsets, rather than modems.
Quite a number of people have the combination of separate voice phones and data devices - perhaps using the data device only during working hours for email / web etc. And there are also plenty of people like me "in the industry" who want to play around with new mobile apps, but don't want to install them on our primary phone - and there's no point having a full voice+data contract on 'spare' device.
Up until a year ago, T-Mobile used to sell Web'n'Walk on a data-only/data-mostly package, which bundled some minutes in, but which was primarily aimed at Internet access. (I;ve still actually got one of these old tariffs, and I daren't try & change it or I'll end up paying more). They've subsequently changed it so that it's mandatory to buy a Flext voice/SMS bundle and then get the data access as some form of add-on.
Other operators have similar offers - so for example the cheapest contract rate on O2 is the SIM-only O2 Simplicity at £15 a month, but you'd need an extra £7.50 data bolt on.
So I started looking at the various prepay SIM-only tariffs, most of which are now starting to be a bit more data-friendly. The typical pitch is a cap of £1 or £0.50p for a day's "flattish rate". So Vodafone gives you 15MB, H3G gives "Fair use", and so on. And T-Mobile gives a "5-day pass" for £2.50
But the absolute bargain has to be 3's monthly prepay Internet add-on, at £5.
So I just paid £10 for an anonymous SIM, which came with £10 of credit. I've signed up via 3's online portal for the Internet add-on, and so now I have an unlocked phone with flatrate 3G, albeit with a non-specified "fair use" which I suspect is probably around 1GB a month. And even better, the usual 3 roaming policies apply - so no premium when I'm on another 3 network, and £3 / MB elsewhere (which is still expensive but about half the price of the competition). I'm not going to use the phone or SMS, just the data services - primarily Internet access.
To be honest I'd rather have the same £5 / month data-only service on a normal postpaid contract rather than have to re-activate the Internet monthly, but given that it seems to be impossible, I'll stick with this for now.
It's also got to be a fantastic deal if you're travelling to the UK and have a spare unlocked phone or PDA and want to have mobile web access.