At roughly the same time Cowper was working on The Road to Corlay, Christopher Priest was creating a similarly drowned Britain in A Dream of Wessex.

In this case, however, the island is not a prison but a fortress, a place of warmth and light and joy that is a defense against the cold and forbidding character of his near-future Britain.

When a representative of this heartless aspect of post-war Britain [i.e., Paul Mason] invades the sunny, rural island it becomes, briefly, as grey, polluted and miserable as the realm from which the dreamers are trying to escape.

Wessex is also, literally, a dream island, a piece of the Mediterranean that has been misplaced in southern England, and in this Priest's islomania is on a par with the intellectual mood of post-war Britain...

These are usually exemplars of islomania rather than insularity: he does not want to cut his characters off from society because engagement with others goes to the core of how they reveal their psychology (one reason, perhaps, why twins and doppelgangers feature so frequently in his work).