Let a few pints of milk go proper sour, then pour the horrible smelly shit through the letterbox, it will run into or the carpet or go between the laminate floor, and leave a fucking awful odour for a good good while.

Order a skip to be delivered to the doorstep.

Pay a farmer an extra few quid to get a doorstep delivery of manure.

Write their phone numbers in the toilets of gay bars and motorway service stations.

Advertise their car in the Loot for a bargain price.