You'd think there'd be a uniform standard, but my understanding is that it depends on the location.
In this part of the world, the ROCs and pseudo-ROCs generally aim for two hours on, one hour off (staffing levels permitting). The worst case scenario at my place - if we're missing one of our GPRs - is 3 x 45' breaks, rather than 4 x 60'. We're free to leave the building during breaks, providing the SSM can contact us in an emergency.
We have a tuck shop, fridge and (sometimes) an espresso machine on the operating floor and we're all expected to make at least one round of hot drinks per shift. Takeaway deliveries and team meals are not uncommon. If we need a short PNB, the SSM or neighbouring signaller will watch the workstation. Ditto fag breaks.
I suspect we probably get a pretty good deal compared to some other locations/areas. I believe the minimum entitlement is much less (2 x 20'?) and judging by our internal forums, some other ROCs are much closer to this. I've seen posts by people at Edinburgh and Cardiff complaining that they've only had 1 x 30' or 2 x 20' breaks, and TVSC (Didcot) have had to close workstations on at least a couple of occasions this year to allow signallers PNBs.