30p FOR A DAYS INTERNET FROM MIDNIGHT TO MIDNIGHT
This seems a good deal as you get up to 24meg for 30p - but then it charges you at £2 per meg. However, using a mobile it would be virtually impossible to do this unless you were using it for downloading etc - normal browsing and emailing even with fairly normal attachments would not come near this limit.
Even if you are just using this for web based texting it could save you a fortune (which also works favourably with the £5 per meg if you used them for international texts while roaming).
It works with messengers too - so if your phone can run a messenger you could keep it on all day and not get anywhere near your limit.
It also works with Google maps, including the facility to act like a badly estimating sat nav (its telling me I am 150 m from where I am just now), but this could be quite data intensive if left running all day while travelling so could reach your limit (but would be fine for letting you see where you were on a long train or bus journey if you only used it as you needed).
Additionally - Virgin are charging £5 per meg for international data - which although seems a silly price - is the cheapest of the companies I have looked at.