Britrail pass?

[Colin]

Take the coach. It's cheaper and still very efficient.

Unless you are used to driving on the left of the car I would advise against it, especially in the bigger cities. Sit back relax and let someone drive while you enjoy the view.

[JS Sanders]

To save a considerable amount of auto insurance, charge it to your American Express card. Doing so provides trip coverage & saves a beau coup of cash.

There are a few caveats, but easily met if you know before you go.