Save your congratulations, I don't deserve them—it was a Minor Victory on points, and that after many unsuccessful starts, switching AI from Colonel to Lieutenant and from Hard to Normal Activation Bonus and, in this game, reversing bad outcomes on two occasions.
It's a rough start for Chuck 1! Oxford seems right out against a competent human opponent wielding Cromwell. I think I suffered more from supply and replacement scarcity in this game than in any other AGEOD title—mostly in a fun, hard choices kinda way, but an advance from Cornwall seems utterly doomed. I either built a depot with those supplies and turtled up in Truro, or those troops eventually starved and offensive operations of any kind only sped up that process. My supply situation pre- and post-London was as night and day!
Is there a winning strategy for the Royalists against a human player? I was able to take and hold Oxford and eventually London only at the expense of almost everything else except York, Lancashire, Cheshire, and the tip of Cornwall.