Installing cat flap through brick wall

hi all

I'm looking to install a cat flap and was wondering on the best approach and tools for the job.

The cat flap will be going through the garage wall which I'm assuming is single skinned.

Would I be best of using one of the following

1. Angle grinder with a diamon cut blade
2. Wall saw
3. Drilling loads of holes and the use a breaker with a chisel bit attachment

I was leanings towars the angle grinder but not sure what size disc I would need to get through the brick. The hole needed for the cat flap is relatively small so concerned that a bigger diameter blade will be too big.

The other option was putting the cat flap through the garage door. Due to the door being so flimsy it would weaken the door even more so I've ruled it out.

Easier to strengthen the door, can't see how a cat flap would weaken it? If you must, drill a hole at each corner and then small grinder to join the holes from both sides, also on diagonals,will not penetrate completely but should allow you to knock out a tidy square hole.

It depends what tools you have - I was taught to use just a hammer and cold chisel but it's a damned sight easier to pepper the wall with holes using an sds drill then break out and tidy with the hammer and chisel