Ok, so it wasn't really much of a road trip, just a weekend train trip to England.
HOWEVER, if you are into Roman Ruins, I can heartily endorse taking the train to Hexham and then the AD122 bus out to Hadrian's Wall. It's a pleasant journy and there are actually a number of different stops (some with museums) on the AD122 route. I only had the afternoon, so I went to Vindolanda. Amazingly preserved, great fun people-watching, and a lovely little cafe. A few re-created buildings, and an impressive museum of artifacts.