Something interesting I found when doing an experiment as england on M/VH
before waiting for the patch but it shouldn't matter when it comes out.

The council of nobles will provide you with missions that usually provides you with mailed knights and I found that early in the game, mailed knights are very very useful, especially against the scottish and rebels. Ratio in my armies were at least 10:10 with levy spearmen and archers which are easy to get. You can quickly build up armies this way.

Priority first is to take control of the English isles ASAP. That means conquering all nearby rebel settlements as quickly as possible including Dublin. Another good idea is to send your princess down to France and marry to solidfy an alliance with them.

At the same time, have your continental army take control of all of the surrounding rebel towns. Once your alliance is made with France, you should be okay for the time being so long as you maintain decent garrisons. Which I should also add the rebel towns are quite strong so you'll need to either starve them out or increase the army's strength.

I decided to turn the continental settlements into fortresses since their the most vulnerable. I gathered whatever remaining troops I had in England and launched an assault as quickly as possible on the Scottish main captial. The Scots had been passive for the first 14 turns by building up their forces and readying to attack the other rebel town up north so the captial was weakly guarded by two generals and spearmen. I had a spy open the gates and quickly attacked the first turn. I sent militia spearmen to wear down the generals before sending in the levy spearmen followed by 10 mailed knights.

As a result I wiped out the Scottish without angering the Papacy since it was quick and short. Eventually the last rebel town will be taken in the next few turns. At this point, I made sure that all settlements in the English isles were turned into cities since they are the most safest. By Turn 15 I had control over England with cities pumping out money and the 3-4 continental settlements acting as fortresses and the Pope loves me the most.

I quitted the game as this was an experiment but I found that due to the speed, the HRE was keeping the Danish busy which left the two rebel towns up north of it open for the taking. If you can take these towns quickly, you'll add onto more, you'll receive greater control over the northern sea and areas remote enough to keep it safe. Plus, you can wipe out the Danish which should be weak by pulling the same strategy, either with siege weapons or a spy to open the gates. If you can wipe them out in one turn, the Pope won't mind.

This allows you to assert dominance in the north western section of the map which is a good position to start out from.