Max;114838 wroteGood news for me - Torx spanners arrived.
Bad news - the front bolt on the thermostat housing is now rounded within. Minor job turning into major and rain predicted for today.
I really don't feel like drilling the head off and hoping I can remove the stud sans dropping metal into my waterways!!
Gosh I dislike Phillips heads and now Torx!
Impact gun and impact bit is the only way to do them
Otherwise they requently round off as you have found
Your probobly struck drilling the entire bolt and then re threadding it
Ive done this a few times now with 100% success rate