Orange has restricted my bandwidth

Hi, bear with me please as I am a newbie and non-technical!
I have been with the same company from the time it was Freeserve through its various takeovers etc and is now Orange, and have never had any complaints or issues with them.
I now have 2 teenagers who are constantly playing online games, watching iPlayer, Youtube etc. Last month I had a letter from Orange saying that I had exceeded my limit under the fair usage policy and if I didn't behave then my bandwidth would go down - which it has done tonight, I'm getting .5 mg rather than the supposed 8mb..
What do I do? Ask for my MAC and threaten 'migration'? What company would I go to that would tolerate heavy usage without charging a fortune?
Would be grateful for your advice, thanks!

Who has LLU prescence at your exchange?

What exchange are you on?
http://www.samknows.com/broadband/search.php

Do you know your line stats - Attenuation and SNR Margin?

My exchange is Fishguard. Sorry, I don't understand any of those terms!

You don't have an LLU choice at Fishguard.... Lovely place though.
So it all depends on how much you want to pay and how much data you shift at what times of day.

Oh, no LLU. You're stuck with choosing different flavours of BT's wholesale offering, sold by various ISP's.

Is there anything special you rely on Orange for, that would hurt you if you lose it by migrating to another ISP?

I guess most of the usage is at peak times, evenings and weekends. I'm currently paying £18pm so would not want to pay more than around £25. I've looked at UKonline, but they, and presumably other companies, say that there is a compulsory purchase of a router for £50 - I wouldn't want to pay that either.

You would need to buy a router or at least a modem as the Livebox is restricted to Orange users. It can be unlocked but frankly, it's not worth the hassle.

Would you want that £25 to cover just the broadband costs or does that include a phone deal?
Would you want email or webspace accounts?
Do you or your kids use P2P apps such as Limewire or Bit Torrent?

Whew - things I hadn't considered!
I don't need a phone package so it would just be for broadband
I have a Belkin router which isn't locked to any provider.
I suspect that my children probably do use Bit Torrent etc despite dire warnings from me.
Email - not bothered really as there is always hotmail to fall back on. One of the reasons I have stayed with the same ISP is to save the hassle of changing addresses, but I guess the time has finally come...

I'll work out a few choices for you later.