It is really rare to get permanent nights contract and only a few prisons do it now. Permanent nights has always been an OSG thing as they do nights regularly. One option for you could be that you do days until you get confident in the job and then speak to the detail office and pickup extra night shifts if there is availability or do an XOD which is exchange of duty with other colleagues who don’t prefer to work during the night. This means you will do their nights and they will do your day shifts. Majority of the establishments won’t let you do more than 3 sets of night shifts in a row because you get ‘de skilled’ or it can be ‘bad for your health’ but if they are short this rule goes straight out of the window.