Truro is *in* Cornwall (Cornwall is the county, Truro the town). I've never used the eurorail site, as Railtrack is going to have the most up to date information for travel within Britain.
Hope you enjoy Cornwall, it is a lovely place, especially if you like the sea - beautiful craggy coastline with cliffs and rocks. There are some beaches which are really good for watersports such as surfing/windsurfing although the sea will be very cold at this time of year.
If you're not too worried about your cholestorol levels, try to have a traditional 'Cream Tea' while you're there. Any teashop will do one, it's a regional speciality of South West England. Basically it consists of a scone (a sort of dry bun, sometimes with dried fruit in it, sometimes plain), a pot of jam (jelly!) a pot of Cornish Clotted Cream (like really thick cream with a crust on top) and a pot of tea. Sometimes you get sandwiches or other cakes as well as this. Mmmmmmmm, yummy!
Cornish Pasties are another local speciality - you can get pre-packed chilled ones all over Britain, but try to get one from a Cornish local bakers shop if you want to try the best. They are a crusty savory pastry filled with meat and potatoes. They have a large ridge around the side - traditionally they were baked for miners by their wives, and the miners would hold the ridge with their dirty hands, then throw that bit away so they didn't get their food dirty. They can also be sweet with fruit fillings too.
If you want any more info, just ask!
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Time is an illusion. Lunchtime doubly so.
Epona of The Laughing Hyenas.