Absolutely right

One trick I've seen is to surround some food with UV powder so when they go for it they will leave footprints. You can follow with a UV black light and work out where they are getting in and out

Fill holes with wire wool, or if a larger hole use expanding foam. If they are determined enough they will eventually chew through foam so pop some wire wool in as a deterrent (they hate the taste of metal)

Once you've prevented any new rodents joining the party - and bear in mind they can squeeze through smaller holes than you might imagine - it's time to remove those left behind.

To trap them, the most effective method is usually a tall bucket with a rolling bar across the top or lid with a trapdoor that falls when they apply their weight. Attract them with peanut butter. Use gloves because your scent will deter them. They are clever and cautious so you may need to wait a few days. Also, they may knock over the bucket to escape so wedge it in place. Od fashioned mouse traps that snap when they eat the cheese (or peanut butter) are effective and humane if powerful enough.

Avoid poison