Sat Nav advice please

I'm after opinions and advice regarding dedicated sat navs. I have been a long term user of TomTom sat navs, having upgraded and replaced several and always with TomTom. Last week i took the plunge and bought the Camper & Caravan edition from TomTom. We used it this weekend for our trip out to Woodhall Spa, a place we have been to previously so thought it was a good test route for the new device. To say we were dissapointed is a massive understatement. On our outward journey it took us over ten miles 'round the houses' and added approx 20 minutes to the known route. Worse was to happen on our return journey, as a result of the experience of the outward trip we calculated the car and van route and then compared it with the lone car route option. The result was staggering. The car & van route was in excess of 14 miles further and a massive 40 mins longer. Taking into account the calculation of time would be based on 70 mph for the car and 60 for the outfit, i still estimate a good 30 mins extra time. To compound matters the lone car roouite was on good roads with no country type roads, no narrow road, low bridges tight corners etc. etc. We elected to follow the car only route and had a dream journey home. Needless to say the TomTom is being returned to the seller for a full refund under their 14 day satisfaction garauntee.
The point of this essay is this, does anyone have any advice and or experience of a reliable tried and tested sat nav for caravan touring and could they make any recomendation for me to take a look at?
Thanks in advance
Ray