Hi and welcome to the forum.
Sadly the advertised numbers are unattainable in reality and these days the small print does point out that the numbers are only useful for comparison purposes.
A real-world 60mpg is reasonable from a D2 but it depends on driving style. Sit at a steady 70mph on the motorway and you'll get high-ish 60s.
Some on here have achieved high 70s mpg but it comes at the cost of driving very carefully with climate control off.