Companies that have cottages in Northumberland

[Hyperhypermum]

Having an absolute mare finding a cottage in Northumberland this August. All the suitable ones seem to have gone, like this one www.gracedarlingholidays.com/cottages/isobel/

I've tried most companies such as Hoseasons, Cottages4you, Northumbria, Coquet. Any suggestions where else I can try. Have I really left it too late???