Using mobile phones abroad

OK, everyone knows this sucks, but I'm going to write a brief rant anyway.

Especially having a smartphone, I don't plan to take my contract SIM away with me. I don't want to come back to an enormous phone bill because the phone decided to download some update or something while I'm away.

But even ignoring that, my contract is absolutely appalling in the regard. T-Mobile charge £1.50 to make or receive a call (I assume per minute) and £7.50 per megabyte of data.

O2 pay as you go charges £6 per megabyte of data and 99p/minute to make calls to UK mobiles/landlines or receive calls. Still absolutely insane, but way better than T-Mobile's contract rates, and of course with pay as you go I'm spared any nasty surprises.

I had an O2 pay as you go SIM when I did the 2010 trip, which apart from the byzantine calling process, worked out pretty well.

I haven't gone exhaustively over the other mobile providers, partly because I sort of feel I can trust O2 to work (though things might have changed since 2010, of course). I did have a quick look at Vodafone, who (concentrating on data; it's the main use I expect, except for emergencies) can't express themselves clearly. On pay as you go, it's £3 a megabyte up to 5 megabytes, then £15 for every 5MB after that. Ignoring that frankly underhanded switch to billing the same per-megabyte rate but in 5MB chunks, that's a pretty good rate. But they also say that pay as you go customers will *automatically* benefit from Vodafone Data Traveller, which costs £5 each day you use it (UK midnight-UK midnight, which is great when you're abroad - why not give a 24 hour period from first use of data instead?) and gives you 25MB allowance (for that day only, I assume). That seems contradictory to me. If VDT is automatic, in what sense are they charging you £3 a megabyte up to 5 megabytes?

Oh, and they also seem to imply simultaneously that only certain countries are "VDT countries", and then they say it applies to the "rest of the world" at a higher rate (which is the price I quoted above, since Chile is "rest of the world".)

So they can get stuffed. I've ordered a free O2 SIM.

(Massively confusing Vodafone page is here: http://www.vodafone.co.uk/personal/price-plans/managing-my-costs/travelling-abroad/using-the-internet-abroad/index.htm)