What will happen? (I'm just curious)?

[David]

I might be changing my internet service provider (ISP) from bt to virgin. What does the old one do with your internet history? and will they only give it out if you ask for it?

[Southpaw]

They are obliged by law to keep it for many years and they will only reveal it if people in authority demand it;
https://www.gov.uk/government/news/commu...-the-facts
Only the addresses are recorded, not the content.
The content may be retained on your PC though unless you use "in private browsing".
Unless you ask for a breakdown of your bill from your ISP then rather like itemised billing on a telephone line you will only be able to access it if you are in a billing dispute.
Regards, Bob.