[migrator]

Is this the time for a good supply of the magical WD40 or similar?

After a good soaking, try a sharp rap with a hammer (downwards, not sideways) and then use two nuts to lock on the stud prior to turning it out.

If one shears off, you can use one of the others (or a new one) to guage a drilling depth. Drill out the centre of the broken stud and then then tap in an old screwdriver blade to assist in turning the stud loose. I have taken out broken bolts/studs in the past in this way.