Your 120-mile commute definitely sounds better suited to a diesel. DSG gearboxes can occasionally be a bit sluggish off the line, but it's worth bearing in mind that they do adapt to your driving so, with time and a few miles on the clock, it should become a little more responsive. There are companies that specialise in remapping VW Group diesel engines - doing so will make the car more responsive off the line. They'll tweak the DSG gearbox's change points, too, so it'll be less inclined to needlessly hold onto gears. It's worth bearing in mind that going down this route might invalidate the warranty, however, and you'll need to inform your insurance company.

All that said, don't necessarily write off the idea of a PHEV straight away. If you can charge a car at home, you can expect to cover 20 or so miles (in the real world) under electric power - a substantial chunk of your local journeys. It'll be a bit thirstier than a diesel on your longer journeys but it'll be worth looking into charging at work, if that's an option.