A check of your deeds may be educational. There are two common layouts for terraces, one is with an alley/ginnel/back entry/snicket/whatever you call it between the yards/gardens, but the other is with a through right of way for residents right next to the houses and the garden beyond (this type is particularly common in Lancashire). People have tended over time to block these up, but the right of way will usually still exist.
In the 1960s Council blocks where you had terraces of 4 houses, the inner two generally had right of way through the garden of the outer two, though many have an arch in the middle instead.
There are very few where, at construction, there was no right of way, other than those where access is through a garage.
Of course, while you could go to Court to assert that right of way, it won't make you popular!