What are Spain and Turkey doing while GB is running rampant in North Africa. If I was a Turk/Spanish player I would be pointing out to the British that it was not in their best interest to get to greedy in North Africa. A Brits nightmare in this game is a French/Spanish coalition. It's not to hard to send a Spanish fleet to Africa with a French corp or two, plus a good French leader. The Brits don't have much for leaders early in the game. Then, of course, the Brit has to garrison Gibraltor well if the Spanish player is hostile to him! Or, with creative players, Turkey and Spain could form an alliance to contest GB in the Mediterranean. Lets see how long Britain can keep the French blockaded when he's having to commit navies to counter a SP/TU coalition!
GB can probably obtain a province, maybe two in North Africa, but only with concessions, and deal making with the Spanish/Turks. This is especailly true in the early stages of the game when the size of the British army is pathetic. In the many games I've played I have never seen the British obtain much in North Africa. I would suggest perhaps that your SP/TU players were intimidated by the quality of GB troops. Unfortuanately for the Brits, they can be attritted down to nothing pretty quickly. Plus, their superiority in morale can be offsetted by cavalry superiority, which either the Spanish or Turk can obtain against him.
Hopefully this will give you an idea how to counter this dilemma you have posed!
French Player in Going Again II 1792