http://www.dailymail.co.uk/news/article-2397842/Inside-eBay-train-thats-converted-luxury-accommodation-railway-enthusiasts-Cornwall.html

We stayed in the TPO (located at St Germans) about three years ago.
It really is a great place to stay and right by the main line. Being in Cornwall however, the variety of rail services is limited.
Good fun and St Germans is in a lovely area. Nice little pub offering good food in the village.
Great to wake up in the morning and watch the trains passing.