Which Tractor Unit???

[Twinpipe]

We're getting a trailer built and need to find a tractor to pull it. I'm a bit out of the loop on these things so I wondered if you guys could recommend something.
It'll probably be a few years old but with fairly low mileage and the trailer will be 40' long but no more than 20 tonnes.
Prob a 4x2.
Who are the best manufacturers at the moment and what models?

Cheers guys