I think because it is week in week out that Sundays have to be worked on then it is deemed normal for the job and therefore your salary covers this.

The big issue is work life balance, I work in an industry where traditionally people work very long hours and we now have been banned from working at weekends and after 7pm in the evening without getting express permission from a senior manager and it really has made a big difference. I think your company needs to restruture its working practices as soon as possible (until you can renegotiate your contracts this will not be possible) to give people time at home.