Any ideas?
Not my doing but one of the screws in tap is seized and head destroyed.
(see image)
I have carefully tried various cross head bits and needle nose pliers.
I have currently sprayed with lub to soak overnight.
Access is not good as it is recessed by 12mm and the dimaeter of the
access point is 12mm.

My next attempt would be to drill out but want to leave that as a last
option. So any other ideas to explore first?

https://imgur.com/ZAjiiIG