Looks like they'll be starting out with letters at first: http://www.independent.co.uk/life-style/gadgets-and-tech/news/pirating-tv-shows-films-illegal-download-recieve-message-isp-internet-provider-a7531276.html

Internet companies send letters to customers who have been downloading pirated content

Sky, BT and Virgin Media are getting in contact with customers from today (17th Jan 2017)