"But it is noisy distracting full of movement and can affect office routines."
I don't know what this particular man is doing, but a quick check with my Muslim colleague tells me that the prayers are silent and the movement no greater than someone doing physio stretches. If a colleague had put a shoulder out I wouldn't stop them moving in similar ways at regular intervals.
Sometimes things happen in offices that can affect those office routines. It happens. A big part of working in an open plan office is learning to deal with these distractions as and when they happen.
British culture is changing all the time, not just through immigration and absorbing other cultures, but also through it's own normal social development. This is why it's no longer the norm to, for example, smack an errant child.
People, in fact each individual person is going to have some sort of take on some sort of theism or philosophy. There's pretty much no point in trying to convert any of these individuals to another point of view - they'll either believe it or they wont. There's no point in banning all religion or insisting on religion; you can't force belief and there's no point in pretending either way.
Having accepted that whatever rules or edicts are passed, people will believe (or not) in whatever they believe (or not), you have to work out how to deal with the implications of that.
The assertion of 'no - you can pray but only if you do it our way' can be extremely limiting to the workforce. I personally prefer the option of 'you can pray in whatever way you choose as long as your designated tasks are completed on time'. It widens the potential workforce to those who wouldn't otherwise be able to work for me.
I just think it's more productive to say 'your culture requires x, mine requires y - how can we make them work together?'. This is just my opinion though.