Having got the car back, everything was going smoothly for a few months.. 

Until I turned the key, and smelled fuel.

Knowing instantly what had happened, I opened the bonnet, and found a spray of petrol shooting out from a gnawed hole in the injector line, to the centimeter where it had been chewed out 3 months before.  Not happy.  

So, the car's back at the shop, the shed's been emptied out and the surrounding garden cleared of old piles of tree clippings and mowed grass - with the help of a 4 cubic meter skip which we filled to the brim.  

Baits were laid, and after the first few days, they stopped disappearing overnight and the little piles of rat crap began to change to a weird iridescent green color, similar to that of the baits themselves.  Finally, yesterday, no baits were taken.

Meanwhile, Brian's car's in the back yard.  For the first few days, whenever the baits were taken, we'd find them arranged neatly under his bonnet, sizable chunks taken out of the blocks and some of his wiring.  Nothing fatal as far as the car's concerned, but we're not risking being completely sans-auto, so it stays there until mine's back and we can take his in for repairs.

Sneaky little bastards.