They are very much, "here today, gone tomorrow" companies.
Mostly their guarantees are worthless because they disappear so quickly.
e.g. Relative bought a property that had had damp proofing injected twice in
the previous 10 years.
Neither company was still trading; under their old names anyway..and a
proper survey showed the damp was due to rainwater penetrating the render.

Mm, my last acquisition came with a 25-year guarantee which was
ceremoniously handed over at purchase; somewhere in the small print it
said that liability was limited to the cost of the chemicals used if
they are proven to have failed (and that's just chemical failure, not
the technique used); it doesn't cover the labour cost involved. The
company who actually did the work, and who "guaranteed" the labour, is
needless to say, long gone. All part of the Great Damp Scam IMO.

David