rail pass validation

We validated our pass at the first station we departed from in the UK

You are talking about a Brit-Rail pass, right? You can't validate a Eur-rail pass in England , they are not valid there.

If you use the Heathrow or Gatwick Express, you can have your pass validated at Paddington or Victoria Station after you arrive.

If you have a Eurail pass and you want to use the passholder fare for the Eurostar to Paris, you can validate it in UK at the Eurostar station.

If you can get to a station before your day of travel, you could get your passes validated and not have to worry about lines, missing your train, etc. You can request seat assignments at the same time, if you know which train you'll be on. Most of the time the station lines aren't bad, but we got stuck waiting over an hour in line at the Edinburgh station! The other thing we noticed was that sometimes no one even checked our passes on the trains!