Wow OP, you're getting a total hiding here. I don't think you're being unreasonable.
Only the courts - or through mediation - will you be able to agree the exact amount, but I don't think it's unreasonable to expect some amount of spousal maintenance on top of child maintenance. You had what is classed as a long marriage (10 years), have a child together, he earns almost 3 x what you do, and you will be in sole charge of the child for most of the time. Plus you'll need to house 2 people in London, which is bloody expensive, while he'll only have to house 1 person (with room for your DC to stay a night or two per week I guess).
I don't think you'll be able to get money to cover childcare as well as spousal maintenance (it will probably be included in whatever child/spousal maintenance payments you agree) but yes, why should you shell out hundreds in childcare every month to enable you to work when he bears no such costs?
And to people not living in London, £650 pcm is not at all unreasonable for wraparound care, especially when you factor in commuting time. My wraparound care comes in at £800++ a month (for 2 kids) - and I only work 4 days per week. Don't forget this includes babysitters when you go out or need to work late etc, all costs that your ex presumably won't have to bear, or at least not to the same extent.
I don't know if you'll get all what you're asking for, but you're not being greedy in my view.