Each force is different but when I done my speed awareness course it was a flat 3 miles
All this talk of 3 miles plus 10% means diddly dont speed full stop if you do and get caught dont bitch about it, Most people drive for a living so doing 30mph will still get you from A-B but without a fine is it really worth it
Built up areas, yes they should have loads , motorways and most dual carriage ways even, are just for money.
It does irk me but if you do the crime then you have to do the fine unfortunately.
In London I got caught buy a camera in a box junction and paid an £80 for my trouble . I wasn't in the junction for the fun of it there was a lorry in front of my and the traffic stopped and I was stuck. I feel that one was harsh.
I always thought it was 10% never heard of the +3 on top though.
Can't believe what they have done near Birmingham now with the average speed cameras on a 30 road lol, I think everyone speeds it's just another money making scandal from the government, if they don't already get enough from us in car tax and petrol tax, they can't even fix the roads already as it is!
If they're in that much of a rush to get somewhere they should set out 10 mins earlier