Will I damage the damp proofing by drilling hole in concrete floor to bolt down a squat rack I’m in the uk?

won't be a problem if you fill the hole with kitchen/bathroom caulk before you put the bolts in. the bolts will squish much of the caulk out [or down], so I'd likely fill the hole only half way. [roofing tar would also work, but its pretty messy.]

yes you will be there is an easy fix to cure the problem, drill the holes , then fill each hole with expanding filling foam.. then use what ever fixing you need to fix the rack down, you must be quick after filling the hole with expanding foam, the material can go off very quickly.