I seem to remember that Scottish Centre will only give RIS in class G anyway, but as their primary task is controlling traffic in regulated airspace and providing Air Traffic Advisory Service on notified specific routes, they may not have the capacity to handle traffic in class G. There is a notified class D airway from Teeside to Aberdeen though, but maybe the captain didn't want to climb that high as the main base level appears to be 155, lowering at each end.