Indeed. the unions preserved industries - docking and hot metal printing - well past their sell by date. With unions in the post office no doubt only ISPs with a union stamp could have transferred emails.
And that mean far far greater suffering when those industries finally closed.
If they had taken a view outside the narrow one of 'fighting for the jobs we already have' to 'doing what is right for the country, and organising ways forward for our members who won't be doing those jobs in future' there would have been no need for Thatcher at all.