If you go to
www.caa.co.uk and do a search for "CAP 371", you can peruse the legal FTL's for flying in the UK. Many UK airlines basically work to this on a day-to-day basis. Some have agreements with pilots that are more restrictive (eg more days off) - some agreements aren't more restrictive, though de facto the pilots don't work to the limits of CAP 371 (eg fixed 5 on/3 off patterns - about 11 days off in 28, rather than the 8 that CAP 371 says).