Oven not heating up?

I replaced the element a few months back on my Neff U1721. This sorted the problem out. Unfortunatly the problem has arisen again. Using my new found skills of element replacing i took it out and it looks physically ok (no evidence of it blowing). Rather than replacing it (at a cost of £30) i have thought that it might be the thermostat. Just prior to it failing to work the oven was fine and heated up (with dinner inside). When we came to get our 'cooked' food out the oven was warm but not hot. it has since not got anything other trhan cold (the fan is working fine). My questions are: If it is the thermostat, would the element simply get hot then cut out or not work at all? Does the fact that the element is not getting warm/hot at all indicate that it is the element? Would the element always have some signs of damage if it 'blew' ?
Any other advice on this matter gratefully received.