Im sure alot of the operators really dislike the MARGO restriction, whenever traffic allows we try to be as flexible as possible.
The MARGO restriction has 2 main objectives.
1. Aircraft ware forced to be within suitable level bands to allow easier sequencing and speed control into the Scottish TMA airfields.
2. At such times when the oceanic track structure is through Scotish airspace then this enables the hight sector (Dean Cross sector 135.525) to get the aircraft below the crossing transatlantic traffic. This increases capacity and reduces controller workload. This also means that when the Dean Cross sector is split, the Scottish TMA inbounds do not penetrate the Dean Cross North sector (135.855)
Hope this helps