Good morning, I hope to be having a couple of nights in Paris next month enroute to the south and during my time there, I should like to do a day trip from Paris to Chartres, last time I was there was in the early 1970s on a school trip. I have been trying to work out what the fare is in euros, I don't want to pre book, but just buy tickets at Paris Mont Station, when I look on the SNCF Site it give times, then reverts to the UK Sales site for prices in GBP £ 12.50 each way. I don't think those trains are prebookable? they are TER services, leaving at 1006 and returning at 1530 ish. Would these be double deckers by any chance? Can one still buy Paris Metro tickets at STP by the way?