Not being a submarine chaser, I nevertheless couldn't help...

Not being a submarine chaser, I nevertheless couldn't help seeing though not reading the occasional article about the contract with the French.
So, what's it all about? Are we releasing ourselves from a binding contract? How much is it going to cost us?
I've no doubt buying American will serve us better in the treaty stakes than buying French but does this mean we're going nuclear?
If we are, does this mean we might also get into nuclear power?