Sync 2 Sat Nav...very odd routes

I purchased a 64 plate mk3 Focis a month or so ago and thought I'd try the Navigation the following day on a trip from Leicester to Sheffield. I've always used Google maps and found it great. I thought I'd compare the car to my phone and thought it strange that there was a 1.7 mile and 6 min difference to the "fastest" route. Most of the journey was Motorway and fast  A roads until it got to the last part of the journey where my phone said 3 miles, 8 mins turning left at a particular roundabout, the car said go straight on, and 4.7 miles and 14 mins, I obviously turned left and having done so, the car recalculated and updated the distance and time to match the phone, these are not new roads at all so I found this odd. 

 

The following day I was driving from Barnsley to Retford and thought I'd check it again, and once more, huge differences, the car said 4 miles and 7 mins longer, again on the "fastest" setting. Instead of going through the village(1 mile) it took me a left turn to a roundabout and up a bypass totalling 2.7 miles coming out at exactly the same place, it also took me 1 junction further north on the A1 when I was going South...bizarre!!! On the way back I did a little test, I had both on the go at the same time, same differences in mileage and time, but I came of the A1 at the junction I know is quicker, and hey presto, the car recalculated itself leaving a 1.7 mile difference(see above re the bypass), again I went the correct way, and the car adjusted itself.

 

To summarise, the Nav on the car knows the roads exist as it did the recalculation, but takes long strange routes.

 

I contacted the dealer who after a little push back, agreed to send an updated v7 card(original was a version 4.1)

 

Fantastic I thought, problem solved....NOPE!!!!! exactly the same, so there is a deeper problem that I need to find an answer too.

 

It's nothing to do with settings, I've been through everything possible.

 

Any help would be greatly appreciated

 

Regards 

 

Richard