I got my info on the train trip from the website below. It appears to be THE definitive website on worldwide train travel. It includes information on the TransSiberian railway.

http://www.seat61.com/Turkey.htm

I agree on the driving but in this case I'm by myself and have to eat up 5 days in Europe so it seems like the best choice. And as it turns out, there do not appear to be cheap airline tickets from London to Istanbul.
On the other hand, there are some journeys for which the train simply has no equal such as the Denver-San Francisco trip.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13