Where is Gormenghast?
In Peake's imagination.
In an article titled 'Burning the Globe' (Peake Studies, vol.8, #2 (April 2003), pages 12–23), I show how it is possible to situate Gormenghast on the map, but this does not mean that Peake intended his castle to reflect anything but what he imagined.
Does this help?
Peter