As someone going through the recuitment phase of becoming a Royal Naval officer and a degree in Physics I'd like to point out that the Vangaurd crash was highly unlikely.
Also to be fair, it proved the point that she is very unlikely to be detected.
As for arguments that the Royal Navy is behind in the Submarine race. I'd bet on an Astute class any day of the week within a years time. The year is for time to iron out kinks and also to get used to using her many inovative features.
If you want to get an idea of just how powerful she is the Seaworth World Naval review 2011 has an article in it on the Astute class. They are exceptionally capable nuclear submarines.
Although the Americans will probably claim the Virginia class is as good I'm not so sure.... Of course the Americans have almost 10 times the number of subs as we do.
Obviously as a game you will have to make sure it is balanced and fun for all

, however from what I know about the Royal Navy, as well as intentions for 2020-2030 I would say the Royal Navy should play the following way.
1) Your looking at a select number of ships, deployed in a very small, compact but highly networked fleet.
2) Royal Navy vessels tend to be specialised with the majority of them relying on the ships helicopter(s) to provide general purpose.
3) Royal Naval vessels have always relied on the belief that strong sensors are far more important than any number of weapons.... if you can't see your enemy you can't kill your enemy.
4) Come 2030 the Royal Navy should have a formidable carrier capability. The QE class will be in service and given that their peacetime aircraft layout is 40 Aircraft you can BET that in wartime it would be closer to 56-60 based on the size and height of her hangers and the deck space available to her.
5) Numbers is where the royal navy should be hit hard. Something that is even harder to plan for when each ship is likely to be more specialised than many other navies based on previous RN history.
6) The Royal Navy KNOW ASW and Submarine operations inside out. The current fleet structure is designed for it. The battle of the Atlantic, The cold war and even the Falklands demonstrated a clear ability in both fighting and using our submarines. There is a reason we call the course you train to become a submarineer "perisher". Those who do fail it are the ASW officers on our ships quite often.
That said, it is of course a game
On that note... how are you balancing the US? She is huge.