Stoves efa700h grill cuts out after around 20 mins, the grill gets very hot, read a cpl of posts about fans and thermo cut outs, easy job? appreciate any help

On the 720 there are two thermal cut outs. Looking at the wiring diagram, the cooling fan and the clock are the only two items that will run independant of the cut outs. So, is the cooling fan running ok or not? If it is and the grill is cutting out, then it could be the thermal cut out that has aged - or the fan may be running slowly because of age or there is a build up of dirt grease under and around the oven and on the outlets that stop air curculating properly.
If the fan isn't running then you need to replace it or the fan timer PCB may have failed. Once you have gotten into the oven's inards, you can test the fan to see if it runs or not.