Caravan Satnavs

I'm thinking of buying the satnav being advertised in the Caravan Club magazine - the Snooper S5450 CC Ventura Pro. We have an old Garmin which, when things go well, it's worth its weight in platinum, which is most of the time. I agree with the argument that caravanners should use common sense and check and plan their journeys. But I wouldn't have foreseen the problems I had getting through Petworth recently. True, the Snooper might also miss the treacherous twists and tight bends like those in Petworth. What to member thinks? Would it be worth the money?