When I travel, I hate waiting, but it's much more palatable if I'm not actually doing anything. It's much less stressful that way. So, hands-down, I loved the option to take trains places instead of driving. Public transportation in the areas of the U.S. I'd lived in before the UK were lacking to say the least, and the train system--National Rail--was a refreshing mode of transport, no matter how much the British complain about it.
We most often took the train in from Cambridge or Ely to London. If you caught the express, the journey took only about 45 minutes to an hour, and that was directly into Kings' Cross. There was no freaking way I was driving around London, what with the congestion zone, tons of traffic, and crazy road layouts, so this was perfect. We'd often leave in the morning on a weekend day, spend the day in London, then come back in the evening. The perfect day trip.
The Eurostar was amazing as well. It's the train that runs from London to the continent, usually Paris or Brussels. If those are your final destinations, great, but you can also change trains and travel the whole continent if you want. The farther in advance you book your Eurostar tickets, the cheaper it is. And it's super convenient--Paris is only a little over 2 hours out from London!
Part of what made the Eurostar so convenient was the ease of going through security. Don't get me wrong; it was super safe, but there weren't the huge lines you'd get at an airport.
Have you had the chance to take some of the trains? How about the Eurostar?
We're winding down, but U is up next, and it's a favorite of mine...