Yokohama W Drive 225/40R18 92 V XL on mine. £128 each from oponeo.co.uk £512 for 4 with free delivery.
used these for 2 years and very impressed. both wet grip and snow is excellent!
Vredestein Xtreme Wintrac 225/40 R18 92 W XL £119 4 for £476 and free delivery.
used these too also excellent.
would recommend either really, i think i paid £600 2 years ago for the Yokohamas and I've still got many years ahead to go!
haven't tried the Continentals 830P but was considering them when i was shopping about. i think they were slightly more expensive at that point so went for the Yokos, but I'm very happy with my choice.