We have just taken on some
self catering properties in St Ives.
St Ives is a lovely spot and I would expect demand for holidays there to remain pretty bouyant, even through hard times. So far this year search volumes have remained fairly in line with 2007, as shown by the google data below for searches on 'st ives holiday', though you can see that searches in January were down.

However, January was down on all the main UK holiday searches, such as 'cornwall holiday':

Demand for holidays, as measured by search volume on key terms, has been slightly down year on year. If you are investing then look for popular places such as St Ives that should remain relatively strong for demand.