1. Yes.
2a. Fill in a GenDec at least one hour before and hand it in to your FISO/Tower (if they do GenDecs for pilots that is).
2b. Telephone LFAT and give notice of your arrival.
3. London Info will say cheerio at the appropriate point, or if they forget you switch over at the boundary ... but it's not an exact science.
4. You can do what you like. As long as you know where you are and can communicate it clearly when you call Lille.
Crossing the Channel is a bit like losing your virginity. Actual event very much over-hyped, but you'll be glad when you've done it.
That's what we did last time (flying that is, not losing virginity) . I welcome other opinions on it, and I'm sure there will be
Enjoy