I do have some sympathy for our friends in the north on this subject. While I appreciate the staffing situation in AC, it has to be remembered that nowhere is exactly overflowing with controllers.
What appears to be happening more and more though is a blanket capping of all domestic LTMA departures. This does seem to be a bit of overkill to me. It would be better if AC could be a bit more choosy over which aircraft are held down. Stopping a D328 or a 146 at FL180 is not much of a penalty for them, whereas forcing a 737 to fly most, if not all the way to Scotland or Ireland at 180 rather than 350 is a bit harsh. This would also produse a fairer spread of the traffic.
If I can just give you one recent example. All domestic flights were capped at FL190 or below. This meant that TC Midlands and the Welin sector in particular were busy. Winding out the radar we could see that Manchester were very busy. When we counted the number of aircraft in the whole of the DTY sector (north and southbound) it was only 5. Hardly fair.