Thanks for playing!
I was really trying to make deck building front and center in this game. If you start aggressively modifying the deck by adding and removing cards, you can start to score 30+ points. If you can get the High Level Mole card to pop up every other turn, you start to score lots of points. You can also get more points for your agents in VP boxes by adding cards to your deck that increase the VP value of the boxes themselves. To get there, you do have to solve some defensive issues first.
Anyway, you ask a great question: what is at stake? Apparently, not much. All these high level moles within the British government do not seem to have provided Moscow with much of value over the years. The UK remained a stalwart member of NATO. The Cambridge Five are, however, a continuing source of inspiration for BBC period costume dramas. The more spies you plant, the more prestige drama you get!