Airblue is not a new airline, they've been around for a couple of years already. However their flight to the UK is relatively new. I think they just started it last year.
I usually fly Airblue when I travel to Pakistan, because not only are their fares quite reasonable compared to other airlines. But their flight timings out of Dubai are also much more convenient than those of PIA or Emirates. The service is not the best in the world, but I don't really mind that since the flight to Lahore is just 3 hours.
The flight from the UK is considerably longer though. They have a refueling stop in Ankara on their way from Manchester to Islamabad and back, because they still use relatively small planes.
I have also traveled with Airblue on domestic flights and they were quite decent there as well.