3G Modems (USB)?

I'm getting an aluminium Macbook and will be using it frequently for college (I'm in the UK).

My question is, I want internet throughout the day so I want a 3G modem. Has anyone had experience with them or can recommend one for frequent web surfing and video streaming via YouTube etc.

Thanks

There are so many variables:
-where you are
- if the provider allows streaming video
- monthly allowance
- how much you want to spend

it's hard to give advice because of these reasons, no doubt there are more too

However, Mobile Broadband Providers is a good place to start