My buddy had rats that lived under this giant wooden framed hottub in his backyard...but then they moved into his garage and used the remnant tubes for the built in central vacuum to enter the house...then it was on. Blocked all entrances with steel wool and putty, traps of every variety (old skool snap, glue, new plastic ones) set up and moved every morning. Highlight or lowlight depending on your point of view was when he found 9 babies in his garbage can. He had no idea what to do...so he filled it up with water from the hose and put the lid to drown them. Problem was he didn't want to touch them when dead...so I "strained" them with a mini garden pitchfork while he poured the water out on his lawn. Fun times.
Anyway hope the rats are gone - and work on finding/blocking entry points (which can be super small).
Also a GBH reference...my old ass brain had them mixed up with BFG.