These are the basic rights in terms of working time legislation:
The relevant basic rights and protections that the Regulations provide are:
a limit of an average of 8 hours work in 24 which nightworkers can be required to work.
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a right to 11 hours rest a day.
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a right to an in-work rest break if the working day is longer than 6 hours.
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So, in theory, your company could ask you to come back in for a day shift, but you cant have worked more than 8 hours in the 24hour period, and you'll need to have 11 hours rest in that period too. So if you did a 4 hour night, and a 4 hour day, its possible, as long as it doesnt add up to more than 8!
http://www.berr.gov.uk/whatwedo/employment/emp loyment-legislation/employment-guidance/page28 978.html