Since April I've been using the iPlayer, BBC website and Absolute Radio's to listen to radio shows/podcasts I've missed during the week.
Today, I received my BT broadband bill they have charged me for over-usage each month since April. 
This is the only 'online activity' I've changed. I've spoken to the BT bods and they tell me it is likely to be down to the streaming sites I mention.
It's cost me an extra £30! 
(I do not upload or dozens of download tunes, videos or programs, either)
You're not alone TB. At Riley Towers we have been managing internet use very closely this month as we've had the warning letter. Our excuse is we have a teenager who has been blithely downloading stuff. That has stopped as we have slapped parental controls on everything. But they don't give much. Apparently the entire monthly usage could be absorbed by 20 hours streaming iPlayer.
Yep- that's what I'm discovering from reading around.
I'm outraged. Unlimited is the way to go, obviously, but that's gonna cost. I'm not sure I like the podcasts THAT much.
Does iTunes use a smilar amount of bandwidth?
I'm guessing a lot of people with kids don't realise how much usage goes into watching iPlayer and YouTube all day long!
Get off BT, it's a f**king rip off. Shop around for a better ISP - there're some good deals out there. And in some caese unlimited means unlimited.
BT is a bit of a rip off
BUT
It's extremely reliable - which is the most important thing.
You get what you pay for!
Our Vigin Internet used to be a bit dodgy but it's superb nowerdays. Couldn't recommend it more.
We're on Virgin. It's not the best, not sure if it's the hub or their end though.
Sadly, the relatively recent development of iPlayer et al means many people aren't aware of the finer details, and perhaps don't read the small print. As has been found out to TopBanana's cost.
Sadly, we're still suffering from the under-investment in our telecommunications infrastructure that BT's privatisation was a part of solving. We got up to speed for phone services in the mid 90s, but the company still hasn't been able to take advantage of further advances in technology, in order to provide us with the connections we need for 21st-Century high-data living.
However, as you're on BT, you're starting off from a reasonably good place. Ask a sales rep if there are any offers on BT Vision at present. The service is essentially Freeview with some extras, including access to 'BBC Replay', ITV Net Player, 4OD and 5 On Demand, all of which provide highlights from the respective catchup services. They've also just launched BBC iPlayer proper, which - as far as I can make out - is exactly the same as on the web. And - crucially for you - all of these catch-up services through a BT Vision box DO NOT count towards your broadband usage.
My parents got a £20pcm DISCOUNT from their BT Broadband bill for agreeing to take BT Vision; so well worth investigating.
I'd advise against making a rash change of ISP, as it can be a very long and painful road - you never know quite what level of service you'll be getting until you've signed up and are connected.
Final point: BT should have been sending you warning messages that you were using, and then had used all of, your traffic allowance. Check your e-mail accounts. If you haven't received anything, please complain to Ofcom, and inform BT that they didn't notify you. They are required to, so it is grounds enough to have your charges waived.
That's some damn good advice.
Great post, Aaron. Thanks 
I'm likely to stay with BT and try and get a better deal off them. This is for 2 reasons: (1) I called the customer service line and negotiated a refund for the over-usage charges and (2) I've been with 3 other ISPs in recent years and had terrible connection problems. I've not had any interruptions in my BB from BT.
Grrr....yesterday I had used 6.2GB of my usage for August (according to the BT monitor). Today, I thought I'd listen to a 45 minute radio show on iPlayer as I still had the best part of 4GB left.
The monitor I downloaded to, err, monitor my usage now tells me I've gone over my 10GB limit
How can 1 x 45 mins of radio streaming do that???!
I'm stunned.
Not forgetting all that porn.
I just got a WiFi modem and piggy back off next doors internet, the cheeky bastard went to bed early last night though while I was halfway through down loading my mid week porn, so there is a down side.
Does he turn the wifi off then?