If it’s Lewisham then you will most likely have met Chris. If not get him round. Our slum landlord next door lets the garden grow for years on end without attention and we have had big issues. Chris was very effective. Repeated applications of poison does help.
If you are looking to block ingress into your home then chicken wire bunched into all holes, nooks and crannies is the way forward. It is awkward for rats to chew (they are very very good chewers), wood, plastic etc are useless. Motar to fill holes is also very good but they can claw their way through old brick and plaster as well.
Nuking from orbit is a solution, quite a final one but a solution never the less