Cutting out at mid temp

[round]

My mk1 gti is cutting out wen it gets to about half on the temp guage (little bit less) it will start straight away but maybe cut out again!
wot could it b ? thermostat ? coil ?anything else ? any help please

cheers  

[Gambit]

is it cutting out (ie stalling) or the revs just go haywire? ie bouncing all over the place? misfiring farting etc

[round]

they drop then pick up then it just cuts out wouldnt say it was missin as such or fartin thou

[sKrEwBaLL]

My mk2 does that, very annoying