Well, I blame it on the G&T.
(even more blushsome, but I am still using my lab's macbook and I swear it has no square brackets so no emoticons possible.)
I was meant to tell you about the bilingual setup here.
Basically, I always speak English to the kids, with a very few exceptions (when I am actually addressing everyone present, or when we are having a joint conversation with someone who speaks no English; recently I have also given in to DS1's pleas for me to read some books in French he's dead keen on at bedtime, since his dad is never around to do it).
I speak to them lots, and try to ensure DS1 only watches DVDs in English. We don't have a TV, so there is no input there in French.
My Mum comes to see us quite often and I try to go to my parents' as often as I can, so he speaks English to other people than just me, and the last 2 years he has gone to Scotland alone with her for October half term.
That's it, really. It's not always simple, but it seems to be working, as his English is really very good. When he comes out of school he speaks French to me, because he has just experienced everything he is describing in that language, and often doesn't have the vocab for 'telling on someone' or 'kicking someone in the shins', and so on. I just answer in English, and we have a dual-language conversation for that bit.
He speaks English to his little brother when he's with me and French to him when he is with his dad...
TBH, one of the only positive aspects of DH's absence from the home and family life is a linguistic one, as it means the boys get a lot of time with just me.
I think it helps that English as a language has kudos: people are admiring of his ability, older children say "you'll always get good marks in English", and so on. I doubt kids who speak Arabic or the gitans who speak a form of Spanish get the same positive feedback.
I am dreading next year when he will probably start "initiation English" at school, since it is done by the primary teachers with no training and most are not very good and are aware of it. Not sure how that will work out...