The sticking point is that the company want to implement the later
friday and sat night running in with this pay offer, but won't
compromise, and actually offer staff something worth having to
compensate for increased assaults getting home at god knows what time in
the morning etc.

It sounds to me as if the pay offer was conditional on some other
changes which the unions haven't yet agreed, which is why the offer (not
"deal" if it's not yet agreed) hasn't been implemented. Is that right?