Paris is so different to London. Here, everything inside the periph is Paris, and everything outside is like a different world. I live in the east suburbs, 20m RER ride into Paris (and 20m in the car on those rare days where there is no traffic) and you would never believe that my town is just a few km away from one of the most beautiful, cultural cities in the world. There is nothing here, just apartments, houses, shopping malls and delapidated town centres with hardly anything going on.
Whereas London has stuff going on all over the place, in the inner and outer zones. I lived in zone 4 there, and there were destination bars and restaurants, street life, heaving parks, galleries, theatres...the main difference really being the street life. Outside Paris proper, it is non-existent. People don't walk, they drive everywhere. And if you want to go out, or do something of an evening (other than go to your one local restaurant, or to a generic Buffalo Grill or Leon) you go into Paris. It's just not the case in London.
I have friends who live in the west suburbs, Marly le Roi, St Germain etc. While those areas are infinitely prettier and posher than the east where I live, it still seems to be basically the same story in terms of lack of 'life' and vibrancy.
I don't get it really. Why is there not more demand from people living in the suburbs for bars, restaurants, culture, Paris-ness?
This is only tenuously linked to the OP, really. But if you take only one thing from it let it be this: don't contemplate moving to the suburbs of Paris if you already feel lonely in London. Stick to Paris proper. With your budget you can get something nice.