We are traveling to the UK at the end of June/beginning of July. Our ultimate destination is Truro in Cornwall by way of Bristol on the way down. I need to get a train from Heathrow to Bristol for an overnight stay and then take the train to Truro for a week's stay there. From what I can glean from sources online, it's best to take the train from Reading to Bristol by using a bus that takes us from Heathrow to Reading. I'm a little confused on what kind of ticket to get. One you can't buy until 13 weeks before your travel date but it seems you can reserve a seat that way but if you miss it, you are out of luck. With flying internationally, it's difficult to figure what train to take given delays that might occur for the US to Heathrow. Any suggestions
You might want to check the coach out instead as it doesn't require changes enroute. Does a tour of the three main terminal areas, then non stop to Bristol, once an hour. If you miss one you are carried on the next presuming space is available for a £5 amendment fee.
Advance-discount train tickets cannot be used on a later train if you miss your scheduled departure, but a BritRail Pass allows you to jump on any train.The BritRail Southwest pass covers the region you've mentioned, or the England pass covers a wider area (not including Wales and Scotland). Either pass covers you on the Heathrow Express to Paddingtion station, where you can connect to a direct train to Bristol; total travel time under 2.5 hours. Pass options include consecutive-day or flexi-day (spread out) coverage for 3, 4, 8, or 15 days of travel.