Outside meter? Thought so
Virtually every UK house built in at least the last 30years (and many more besides) has an outside electric meter which on it has a fuse that can be pulled. Now, I wouldn't generally want to do that while it's under load but compared to 'cutting a cable' it's substantially easier.
Carry a clipboard and wear a reflective vest and no one would even look twice as you open up the meter cabinet on the side of the house.