We are in the process of buying a house that was built circa 1927.

The Surveyor's report has just arrived and mentions some horizontal
cracking on one of the walls that could be associated with deterioration
of the ties. He recommends a cavity inspection.

What does a cavity inspection entail, is it CCTV endoscope type of thing
or is it more intrusive? No rude answers please :-)

Is the repair of failed ties a DIY job?

I was thinking of drilling through both leafs of the wall with very
slight gradient downwards to the outside wall and then resin bonding
lengths of stainless-steel studding, slightly shorter than the width of
the wall - so as to be able to redecorate/point in. Would this be an
acceptable repair or is there a better way?

Thanks

Steve.