1. Not very efficient
2. Many will find it expensive
as compared to other countries. From my experience, trains have been late 3 out of 10 times.

Now, some good news. You can save

1. If you book in advance
2. If you buy any of the rail travelcards

Here is the time taken for train travel in england from London to other places in England/UK: London to Bath - 1h 30m London to Cambridge - 1h London to Devon - 3h 30m London to Lake District - 6h 30m London to Oxford - 1h London to Stratford - 3h London to Warwick - 1h 40m London to York - 2h 30m

Symbol above is British Rail and below one is the London Tube

These are the various train companies in the UK:

Arriva Trains

Wales c2c Central Trains

Chiltern Railways

Eurostar

First Great Western

First Great Western Link

First ScotRail

Gatwick Express

GNER

Heathrow Connect

Heathrow Express

Hull Trains

Island Line

Merseyrail

Midland Mainline

Northern Rail one

Silverlink

South Eastern Trains

South West Trains

Southern

Thameslink

TransPennine Express

Virgin Trains

WAGN

Wessex Trains

England Train Travel and England Trains