okay, who can help me?

[fox]

(x-posted to hp_britglish, but some of you may know the answer and not be over there, right?)

Uncle Wiki isn't turning out to be of much use here, I'm afraid. It looks to me as if many Tube stations in the part of Zone 3 I'm interested in (Ealing, generally) are on the surface rather than underground. I have narrative need of underground Underground over in that direction; can someone either (a) name for me please a Tube station whose platforms are underground somewhere relevant to West London, or (b) reassure me that even though the platforms are aboveground, there are bits of track in tunnels between, say, Turnham Green and Park Royal?

Thanks, I appreciate it!