What's the milage.?
Did you heard about the seal before?
When warning come up at first?
Just asking for the statistics lol
Avoid driving the car as you may do more damage to the engine.
About the garage, just go or ring couple of them and ask them if they heard anything about the oil pump seal on that car if they sound suspicious or you will notice that they don't know what they're on about than I would suggest to avoid them. Ask them if they know anything about 2 bolts being hidden inside the gearbox / flywheel.
Great tutorial video to help DIY'ers replace this oil pickup seal on Insignia 2.0 CDTI 160 themselves saving hundreds of £'s on dealer costs. If you get the "Low oil pressure" warning you need to replace this seal before your engine is trashed.
It seems very common on the insignia and word is get it sorted before driving the car.