St 170 Blown Out Plug

[KASSL]

Has anyone an idea what could have gone wrong or have you heard of this before.
My 2003 ST170 with 87000 mls blow a spark plug out leaving a stripped thread in the head, The plugs were fitted two years ago and have only done 7500 mls. The car is in the garage at the moment the are going to attempt to fit an helicoil without removing the head. If this does not work is this financially the end of the road for my much loved ST

[MH82]

Would be surprised if the Helicoil didn't work.

Other solution is to replace the head with a known good secondhand one

[KASSL]

I'm hoping the heicoil works without removing the head,
The garage is saying 8 to 9 hundred pounds to re-fit, either repairing the existing head or fitting a replacement head,

[MH82]

What, 8oo to helicoil. Honestly, you need to go to a different garage

[KASSL]

The helicoil with the head in place was successful, plus four new plugs labour and vat £205.
The £800 was if the head had to be removed etc