only just seen this, sorry!
DM - how exciting. Yup - we live in the pas de calais and work in London. We both work part time and dh can work mostly from home, so it works quite well.
You can commute daily, but it would be a slog. I've done it a couple of times for just a day but it is tiring. We are about forth minutes drive from Calais Frethun which is the Eurostar station. At the moment it is 1 hour 15 mins to Waterloo, but when the high speed link comes in (which should be next year) it should be an hour toKings Cross. The downside of Frethun is that there are only a limited number of trains per day (three I think) so you have to be careful with timing. You can also drive to the tunnel and then park at Ashford station, which takes longer but is a bit cheaper.
Schools/health wise, I believe that you can go to school and get the carte vital which entitles you to health care here without being in the French tax system, but I would have thought that you would be better off becoming French tax resident (if you are here all the time you should really do that anyway). You get very generous child benefit (much more than the UK) and if you are not earning for the moment it might be well worth it. That said, I would recommend that you speak to someone about your best bet in terms of tax and stuff. I can recommend someone if you would like. There are various people out here who will help you access the French system who are bi-lingual or speak excellent English. They will charge, but it is quite likely to be worth it.
Also, school isn't compulsory here until 6, but there is free, state nursery provision from the age of 2 if you want it. You can send for as much or as little of the week as you wish. Our ds is only 14 months (although we, too, have another on the way) so we haven't experienced it ousrselves, but there is an English family in the village who speak no French and sent their three year old mornings only. After eight weeks he was apparently speaking French and crying to be allowed to stay after lunch with the other children.
Anyway, as you can see, I've got too much to say on the topic. If you would like to email me, my address is the name of this website with the letters ter at the end @gmail.com.