I really do think that if you work for a large multinational, you need go to the HR department - there will be someone there responsible for your department. Go and see them. There is no point in asking us - your Ts&Cs will be different to many of ours, your company's policies and processes won't be the same as mine. Loads of us work more hours than we should, particularly in the public sector, and most of us don't get the time back - but if I caught someone skipping the first hour of their contracted week on a regular basis, a warning (followed by disciplinary if necessary) would be in order. However, equally, you have a greivance against them for not letting you take your holidays etc etc. You telling them you are changing your hours until they sort themselves out is unlikely to wash in a tribunal, you really need to go through proper channels and with a representative with you, if necessary. Get on the phone tomorrow and see your HR team. State facts, don't complain. Ask for something to be done. Take your emails to your boss with you (and theirs to you).