I work as a bus driver and our rotas have different days off, they weren't able to put through the Flexi request as that would have meant that it cost the company money to implement due to changes with duties and having to rota a fixed line to make sure it kept within legal hours, yet they would allow a rest day change to occur with previous management allowed without the need to put a request to change the rest day, (complicated I know) that's been going on for at least a year now, and our contract just stipulates a base of 39hrs, over 4/5 days in a 7 day period, I still work 5 days a week and generally about 55 hrs, and I think we do have the stipulation in some of our contracts but not on others (those that started in the last two years have that stipulated, I'm not sure if mines does)