Cost of UK Cellular Broadband

I am curently visiting my brother in the UK. He needs a wireless Internet connection for his laptop. He wanted to buy a USB modem. I suggested that he connect using a bluetooth connection with his mobile phone. He agreed but said that there were different rates between the two. I argued that the rates must be the same! What is the difference if you connect to the Internet using:
* your mobile phone to surf the Internet
* connecting your laptop to the Internet via a bluetooth connection with a mobile phone.
* using a USB modem

He has a cellular contract with Orange and the answer to the above is yes there is!

If he:
* uses his mobile phone to surf the Internet he is charged GBP0.04 / meg
* connects his laptop to the Internet via a bluetooth connection with a mobile phone he is charged GBP4.00 / meg
* uses a USB modem he is charged GBP15.00 / Gig

And we thought SA is a rip off!

How they know he has connected his laptop via bluetooth is beyond me, but they can!

The phone doesn't chow up data as fast as a laptop or desktop. Usually we use Opera Mini, which minimises browsing costs drastically. Whilst wep pages on PC's need much data, because of the large displays. There's also stuff like flash, pop-ups, hidden windows, updates that could carry on without your knowledge. Effectively, entering a site like http://weathersa.co.za, is only +-30kBs on a mobile (Opera display settings), whilst it could be in the region of +-200kBs on a PC.

I am not worried about the amount of data.
What I find ludicrous is the different rates for the data