Train and buses, there are plenty, but quite expensive. The underground in London is Very expensive (do not forget to get your Oyster card). Cars: lots and lost of traffic jams in England which is very much like a huge connurbation nowadays.... Sometimes people say that England has become just a big traffic jam!!! It is a bit of an exageration, but there is some truth in it!!!
So Blablacar is a good option. Even to go between England and France. There will be terrific opportunities. Choose the Ambassadors first. They provide excellent and reliable transportation for very little money.