This castle to be mentioned only once by Malory, as a place where Sirs Palomides and Dinadan spent a night.
I would guess it to be somewhere in the southwest. If “Valet” is “valley”, the castle might well be in a mountainous region. Exmoor Forest is very up and down, and Beale-Valet might be or be near to Ilfracombe, Barnstaple, or South Matton.