Re: Best traps
Clearly the OP doesn't know how to safely and legally trap wildlife.
1. Who told you I have used them in the UK. There are other countries where stuff that chews on your cable is protected only if it is a protected species. If it is not it is fair game and sod the humanity of the method :)
2. As far as safety, safety of the humans first, safety of the VERMIN second.
What you forget is that story is about squirrels. Squirrels and doormice are not rats or mice. They are an infestation from hell if you get them.
You cannot safely install any trap in under-floor space or roof space. It is a recipe for removed fingers because people always end up pushing cables through by touch alone. With squirrels and the f*** edible doormice you cannot use bait safely. They will take it somewhere, eat all of it, die in an obscure but warm place (on top of a power supply usually), then rot through and leak into interesting places. Even if they do not die there, they will drop crumbs into the fan grille into that so you will be ingesting warfarin powder when servicing equipment. This is in addition to dropping their dung into it and it carries a set of diseases you rather not know. A high-end respirator becomes a necessity when working.
You cannot use normal traps. They ignore them as they move either high above or in the under-floor/ceiling space. They are not rats that scurry next to the wall. They will do it ONLY if there is no other route, otherwise you will see the f*** jumping across racks. The exception here is doormice which will come and steal the bait out of 90% of trap models in front of you completely ignoring you as an irrelevance.
Last, but not least - due to their hearing and senses being in the same range as humans they are not affected by ultrasound and EMP pet repellent equipment.
So your choices are glue or patience and a pellet gun. The second one is somewhat humane if used correctly, but you have to have no other job but to sit with it in a server room overnight. You are also limited in terms of having a clean shot in making sure there is no equipment behind the target.
Most importantly - once you got rid of them (by whatever method needed) do not hesitate to spend the money on a truck roll of chickenwire and rodentproof the whole place.