In fairness to the employee, he did offer to work Saturday morning instead, but Saturday would not suit the majority of customers or the business needs, so its not really a runner, eg a job might need two people on site at once, so going thursday, coming back friday and then going back saturday will lead to additional hotel bills for employer and also a second person having to work on a saturday who will possibly not want to do so, plus majority of customers sites may not be open.
The more it goes on, it would appear that employee is bluffing a bit because people do not know much about his religion and are very wary of bringing it up. To date once the issue was raised there was a kind of huff taken and issue was left unresolved and "went away" for a time.
Person can be ok for the most part but can then just get very awkward over certain things (thats just his personality more than anything else) whereas with any of the other employees you could say "look I feel you are being a bit unreasonable over X,Y, or Z, and they might say , ok fair enough, or put forward alternative and acceptable proposals, but sometimes this person just gets awkward and refuses to budge on anything, once he digs his heels in.
If there are certain family occassion or religious occassion that any of the staff wanted to attend on a one off basis, its not an issue for the employer, once notice is given and adequate cover for the business is arranged on time. However, having someone who can t potentially attend possibly one/two days out of a possible five is a nightmare.
I think the way forward is to stick strictly to the facts of the employment contract/job and not enter into any debate about the religious side at all. Its really none of the employers concern anyway, all they require is to be able to offer a prompt service to their customers.
I personally feel that the other employees have been discriminated against to date, by being stuck with the less preferential locations and times and have put forward that opinion. I think thats partly why they are starting to voice their objections too. If it were me, I would too.
The way I see it, if it does not get resolved soon, its going to lead to bigger problems with more people involved.
Thanks for all the responses and will let you know how it goes in due course.