Had the same problem buddy with rat's entering the garden from under next doors fence! Filthy things and knawed some holes in the fence too..
As the other guys have said patience really is key, I was getting up before dawn, setting up before getting ready for work in the mornings and only ever shot two, dog killed one and caught one in a rat trap over a few months!
These orrible things really are cleaver, we have two apple trees in the garden and the fallen apples is what attracts them to our garden! I have blocked every hole I could find and pick the apple's up daily but not convinced the have completely gone..
Last month I finished off my DIY build night vision which works great but have not seen any signs of them since I finished the build typical
I would say build your own night vision mate, its cheaper than buying one if your intrested let me know and I will list parts you would need to build one..
All the best foggy..