IMHO
The buck should stop at who ever had the report that asbestos was present and never passed this information on.
I believe he/the company he workers for/owns is the one at fault, now if your boss knew and never passed the information on they he should be paying for all costs incured in my eyes.
I am very interested as to what happens with the HSE on this .
Your boss might be being very optermistic that the site will be deemed safe by next week ! ! and HSE will allow you to return. Can they really make it happen this quickly as to do visits and tests and clean up and retest in lets say 5 working days ?
To go off on a little tangent here, we have had to have some work done here on 2 ceilings because of peeling artex (council property) they sent main maintenance contractor out (very nice guy) who informed us that they could do the make good work but wasnt not allowed to over board as they was licienced to do that, so the arrangements where all made.
The approved asbestos contractors come in, they had the window open whilst working the door open , they brought blue dust sheets up, 1 left still in packing the other was used as a rubbish bag, no masks where used by them and no coveralls worn. These are ment to be approved licienced contractors ! ! ! . Complaints have gone into the main contracor and the council.