I have had success with this stuff- not sure if you can get it in Ireland or what it's even called there - but the 1/4" stuff is small enough that even mice can't get through it
You can staple it on to plywood or a fence - presto, critter-proof
Rats can chew through anything pretty much, but they'd rather not chew through metal
And so we begin slowly turnign a wood shed into a metal shed to mitigate its woodeness
My method is largely to tolerate the little beggards in some regions and reign hell on them in others.