I think you'll find the law states 11 hours between shifts not 7 1/2!!
This is copied from the Direct.gov website!!
Daily rest - a break between working days
If you are an adult worker you have the right to a break of at least 11 hours between working days. This means as an adult worker, if you finish work at 8.00 pm on Monday you should not start work until 7.00 am on Tuesday.
Weekly rest - the 'weekend'
If you are an adult worker you have the right to either:
an uninterrupted 24 hours clear of work each week
an uninterrupted 48 hours clear each fortnight
http://www.minimins.com/slimming-world-weight-loss-diary/187905-jos-journey-infinity-beyond.html