[being ripped off]

Hello, I’m presently living in East Yorkshire & the only broadband supplier I am allowed to use is Karoo, which is part of the only telephone company that I’m allowed to use, Kingston Communication.
When I say allowed, I mean that if I try to get a quote from any other provider, they just shrug their shoulders & tell me that they can’t connect me as I don’t have a BT line. This is for both telephone & broadband.

Today I received a marketing email from Karoo advertising their new broadband packages and I’m not too happy about their decision to limit usage. The package I am on costs 16.99 a month and although the speed check on the Karoo website states
“For postcode hu**** we can confirm your line could support a typical connection speed of 4.5Mbps.”
When I use other connection checkers, it averages at
Download Speed 1467 kbps (183kB/s)

I have lots of problems with my broadband, I get regularly disconnected, it can take up to a minute to display web pages at any time of the day and it can take over 10mins to get through to the customer service line.

The questions that I have are

1) How do I find out my “usage”, so that I don’t over the new limits that they have set out?
2) Is it allowed for one company to have a monopoly on broadband in any area?
3) Is it allowed for a company to “confirm” a connection speed but not deliver it?
4) Are there any legal loopholes that would allow me to use another company?