dead easy to solve this mate, what you do is get a family of cockroaches in there and they will eventually eat the slugs for you, now there may be an issue with the cockroaches not wanting to leave and they may begin breeding, if this happens what you do is get a family of rats in there to chase out those pesky roaches. now ive heard vague reports of rats on rare occasions setting up shop in the kick spaces of the kitchen cabinets and, my, they can breed fast. so what you do is get a kitchen fitting specialist in there to rip out and burn the kitchen units and then fit new ones.
all said, this should only cost in the region of £3,000 and take approximately 12 months to fully combat.
there you go, simples.