Have to admit I'm sometimes a bit suprised about some of the figures punted about and can only assume they are packages provided to entice people to take up these posts.
Its true to say that the cost of living in London is more expensive than elsewhere in the UK, but the average salary in the UK in general is about £22k. I guess your accomodation costs are going to be a major factor in the whole thing as regards to your lifestyle. Thats why I always suggest people investigate communting, although I appreciate its not always that easy when you have to think of your child also.
I wouldn't get drawn into the curtain discussion .... just pull yourself together eh?