The 'Long stay car park' is probably one of the ones they are frantically still trying to build!
Currently there are 2 car parks right opposite the new Terminal, with others under construction just beyond those. Stobart also have bought a large piece of land opposite the Airport (by the McDonalds roundabout) which used to be the park+ride car park for the old Access Credit Card call centre staff, that will be turned into additional parking 'as required.'
In the first instance the car park opposite the terminal can just about cope, and the others are nearly finished.
And at £6 a day and 2 mins from the terminal I'd say its good value compared to other airports.