Ad Astral for my money
Did my CIR with them 17 years ago with RM and if the new guys hold his standard you won't have a problem. They probably wouldn't be as funny as him though. I remember him teaching me NDB intercepts onto an arc and sprouting also sorts of trigonometry then when he saw the look on my face he said " If that doesn't work, try TLAR. With me being more befuddled he explained "point in the general direction until That Looks About Right!"