Imagine if the TransCumbria line were still open...
Among other things, you could have a sleeper. An overnight service to Penrith, Keswick, Cockermouth, Workington, Whitehaven and St Bees would do a decent trade, and you could also potentially route it via the Settle and Carlisle if the Penrith-Appleby line were still open too, though a routing via Newcastle could benefit business travellers. A premium overnight service to the northern Lake District could probably do decently, though admittedly only with leisure passengers.
Penrith, Keswick and Cockermouth are small towns; Workington and Whitehaven are scarcely affluent; St Bees is so obscure I don't even know how to classify it!
If places like Edinburgh, Glasgow and Aberdeen require a massive subsidy to maintain their sleepers . . .