The process for actually dismissing someone in the UK is so long and involved (and involves unions too!), that it would probably never get that far. The boss would be disciplined for religious discrimination long before the employee went. Before you get to dismissal, there is a fairly lengthy disciplinary procedure and suspension with investigation and all sorts. About the only time you can dismiss someone that quickly is if you catch someone doing something illegal and have the evidence to prove it. Even then, you might have a hard time until they were convicted and serving time for the offence...

It gets so cumbersome at times that it's really hard to get rid of someone who is actually in breech of their contract or incompetent at their job.