agency workers and overtime

The company I work for are looking at making redundancies with me more than likely being on the list.
I understand why they have come to this decision but unsure if what they are doing is legal or fair.
A little bit of background info factory is open 24/7 running a 4 on 4 off shift system
what they intend to do is lower the number of employee's on both night shifts to run a skeleton crew enabling them to still have the flexibility required. There are no alternative jobs available.
My question is when they get a busy period they will either bring in agency staff as required or arrange overtime for the opposite night shift.
I can’t say how often this would happen maybe once a month maybe 20 times a month can they do this as in the busier periods the job is not redundant. While in the quieter times there is no work at all.

Hi Blade

It sounds like your employer will be able to justify making redundancies on this basis. It sounds like the new arrangement will be more cost effective for them, and that is the key.

Regards

Pete