I very much doubt it was spot on, I have never driven a car thats speedo was spot one. if it is 15% out I would check that someone hasn't fitted the incorrect size tyres.
It was +/-1mph what satnav indicated. I have no idea what it had done to it but really doubt it ever belonged to the Police
Couldn't do my job without one, I cover the whole south of the UK so cannot remember the exact locations of all the accounts that I look after. lol The speed on sat navs is closer to the true reading but I still wouldn't trust it 100%. All I can say to your last comment is if you are speeding and you get caught except it you were speeding.
I don't drive around for work, so hopefully my android will suffice for my needs if I don't know the way
Sorry this one doesn't tally with the last comment quoted above this one. If the lorries are overtaking you then you are doing less than 56mph as most if not all are limited. Out of curiosity how long have you been driving? as the above quote, with no disrespect, sounds like you are not a very confident driver, if this is the case maybe book some lessons with an instructor for motorway driving, my mum and dad made me do this when I past my test, it was a great help. I say all of this as some one who drives approx 1k miles a week and you can always tell the people who are not happy or confident at driving on motorways or even dual carriage ways.
Thanks so much for that. I've done 10k+ miles on motorways (excluding A/B roads which would be another 10k+ at the very least, so I know my driving well enough to be safe and get everywhere I need.
I do try to stick to the limit (and the silly thing said 70mph NATIONAL SPEED LIMIT when it wasn't eve close, and that was that when I gave up on it), which was the whole point of the question, but perhaps I need to get back to the instructor who made me go at 50 in 30 zone.
Many people go as fast as the car in front, which I somewhat disagree with in some cases (why go at 60 on 3-lane M-way -cough M4 in wales cough-, or 40 in 30 zone (anywhere in Somerset)?). The roads are full of dangerous drivers, that don't indicate, don't stop at lights, overtake from the left, etc - avoided at least 10 of them this week alone.
Also if you think that all lories are actually limited you would be surprised how many are not - particularly the smaller ones - I've been driven in one at 80!.
As to what to get for the car
First aid kit
Hi viz jacket for in case you breakdown.
a decent pair of sun glasses for when the sun is out or low, It is amazing the different this can make to your visibility, I have a pair of Serengeti, not cheap put make driving in the above conditions so much easier.