Where to live in London - need tips!

Dear expat fellows,

I'm moving to London very shortly and I'm looking for a place to rent. My office is actually in Slough, so I'd love to find a place by the western borders of Great London.

Ideally it would be well connected to the metro, in a not too expensive but lively neighborhood.

Please share your thoughts about good locations, house hunting websites and anything related. Every help will be highly appreciated!

Looking forward to hear from you.

Cheers!