A few years ago, I would have considered doing 70 on the motorway as dangerous. Certainly you would have been one of the slowest vehicles (cars) on the road and felt pretty vulnerable.
Where I drive 70 is now amongst the fastest of the main traffic flow (yes there will always be a few in a big hurry).
Motorway / dual carriageway speeds seemed to have dropped by 10-20mph, and I can’t imagine it’s the safety campaigns that have achieved this…
Maybe where you live, but on my last long motorway trip from Edinburgh to south Wales and back, apart from the congestion around Brum and Manc, I’d say most cars were doing 80-90, and a few over 100, based on me chuntering along in the inside lane at 70 in a little yaris.
With the DoT saying 49% of drivers ignore the 70mph limit and the plans for the 80mph limit, I’d say this backs up what i see on the motorways. Guess it might be different in the south with so many people and congestion.