Driving – Highways of the United Kingdom motorway – Speed ​​limit

My TomTom Sat Nav tells you in a useful way the speed limit for the road you are driving, and even though you have a disclaimer that says you can not guarantee the accuracy of the update, I've noticed that all the motorways in the United Kingdom and double The access roads of the roadway and any interconnection route, whether single or double track, are indicated at 60 mph.

I thought that the speed limit for slip roads and interconnections of highways (eg, Highway that connects M3 with M27) ​​would be the same as the speed limit for the highway, which in the case of automobiles, motorcycles, vans derived from cars and dual purpose vehicles, is 70 mph (when you are not towing a trailer, another vehicle or caravan).

I have always believed that the Highway Code is the goal of driving laws within the United Kingdom, but the Speed ​​Limits page does not answer the question.

What is the situation in the United Kingdom?