I have been working nights for 9 years.

I started doing 6 nights a week, 11 until 6, and now work 10:30 until 0630 for 5 days a week.
To be honest I prefer night work, but have seen a lot of people suffering from stress and other illnesses because their body could not cope with the change. You do need to get up and get out just to get some sunlight. The winter months are the worst, going to work in the dark and getting home when its dark, I only probably see about 2 hours daylight in the winter months. If you work nights, any form of a social life will be non existent.
The law (taken from the DTI website) also states the following rights:
The basic rights and protections that the Regulations provide are:
• a limit of an average of 48 hours a week which a worker can be required to work (though workers can choose to work more if they want to).
• a limit of an average of 8 hours work in 24 which nightworkers can be required to work.
• a right for night workers to receive free health assessments.
• a right to 11 hours rest a day.
• a right to a day off each week.
• a right to an in-work rest break if the working day is longer than 6 hours.
• a right to 4 weeks paid leave per year.
You are also entitled to a free health assessment before assignment to night work and thereafter at regular intervals.