UK users and your data usage

So all this talk about data usage has made me think I'm seariously under using phone!

People saying they use 5 to 50GB of data a month seems insane.

It makes a bit of sense when considering movie streaming which seems to be happening in the US. But as far as I'm aware this isn't something available in the uk.

And I guess some users are tethering other devices which would explain it.

The only video streaming I'm aware of is YouTube which over 3g is crippled and doesn't use up a lot of data, and iplayer which is wifi only.

I check and send emails during the day, check facebook, download apps and do light browsing while out and about and I use maybe 100 mb a month at a push!

Basically my question is, what am I missing out on?
Is there a video streaming service I'm not aware of?
Do radio apps take up loads of data?

I ask because I'm paying for unlimited data and don't seem to be using it at all compared to some people here and I find it perplexing!

Sorry for the massive post, but looking for a uk user to put me at ease.