T-Mobile UK is the latest British network to impose stricter limits on how their customers can use mobile data. From February 1, customers will be subject to a "fair use" limit of 500MB, beyond which access to stuff like video streaming and 'file downloading' will be restricted. Currently T-Mobile offers a generous fair use limit of 3GB per month for Android smartphones on their network.

Find out more about how this will be changing after the jump. [T-Mobile UK]

 A recent T-Mobile statement explains the changes in more detail.

"We’ll always let you email and browse the internet and you’ll never pay more than you agree to. We do have a fair use policy but ours is there to make sure we deliver the best service possible to all our customers. This means that you’ll always be able to browse the internet.

So remember our Mobile Broadband and internet on your phone service is best used for browsing, [...] but not watching videos or downloading files."

This is a slightly more reasonable policy than is offered by some other operators, who will cut off all data access the moment customers creep over their monthly limit. It's difficult to see how the network will be able to distinguish between normal web traffic and HTTP downloads, though.

What's more worrying is that T-Mobile says the new limit will apply to existing customers  as well as new sign-ups. Right now, the fair use policy that new customers are linked to still refers to the old 3GB limit, meaning that it'd be possible to sign up to a 24-month contract today expecting 3GB of data per month, only to have it cut to a sixth of that three weeks later.

Competing networks like O2 and Vodafone stopped offering 'unlimited' data in late 2010, instead switching to fixed data limits of varying sizes. However, under British law T-Mobile is free to continue advertising 'unlimited' data access, even with the new 500MB cap, if it believes the majority of its customers will not be affected by the limit.