high usage figures

Compared to 7 years with f2s and usage figures around 10 GB per month I've been surprised to find on changing to BT the usage has increased dramatically.
Nothing has changed here and although I'm now on a 12 day review with them, I've been using the TBH usage tester and find its figures are about a 5th of BT's usage metre.
While the test is on, my sons Xbox usage and my streeming usage has been curtailed so we seem to be using around 1.5-2.0GB per day for sending emails and visiting the web, which in my sons case is mainly facebook and twitter.

any constructive suggestions anyone.

streaming youtube videos etc can eat up bandwidth easy, 7yrs ago I was on similar usage to you and with F2S but can tell you know its well into 3 figures now.

Tweets are so small, so unless lots of pictures/videos unlikely to be that. Facebook similar, unless you are making the mistake of leaving it running with a heavily auto refreshing page when not actually at the computer.

Is this FTTC per chance? Got Skype running?

The tbbmeter View Sites Visited page can give you an idea of what has chewed bandwidth since app started.