My 2 daughters attend a very good private school where the fees are lower than many private schools, myself and my sister also attended as children.
Dudley House School, Grantham, Lincolnshire. Grantham is on the main train line to King's Cross, I believe that it is around an hour to King's Cross. I know many people who choose to live in Grantham and commute to London everyday.
Dudley House School is affiliated to the Seventh Day Adventist Church, but none of my family are Adventists or religious in any way, please don't let that put you off, I know some people have a view that there may be something odd, but I can assure you that is not the case, the majority of pupils are not Adventists, and anyway they appear to be very nice caring people. The school does have a uniform and teachers are not called by first names, but there is something very unique about the school. Many parents now were pupils themselves. Another benefit of Grantham for schools is that there are good grammar schools in Grantham, and Dudley House has an excellent record at 11+.
This is something I recently wrote about the school;
As an ex Dudley House pupil myself, when the time came to choose a school for my two children I was very pleased to find that the same unique and exceptional atmosphere existed as it had done 30 years ago. I believe that Dudley House School is an incredible environment for the very best in education and development for all children. The small class sizes mean that children are stretched academically at their level. Teaching is encouraging and challenging, but also sensitive resulting in bright, happy, caring and confident pupils. My eldest daughter felt completely at home right from the start, she has progressed exceptionally well academically and personally, and my youngest has been desperate to start and finally will in September. The school is sponsored by the Seventh -day Adventist Church, who are Christians, but my family are not Adventists as many others there are not, but actually it is probably the Adventist affiliation that has served to create the lovely calm environment that exists within the school, without there really being anything different to the religious education in the school from most other primary schools. An interesting fact that I only recently found out is that over 100 years ago an Adventist, John Kellogg and his brother were responsible for inventing corn flakes! And with September 2010 annual fees working out at £330 per month spread throughout the year, I see Dudley House as fantastic education for my children, highly recommended.
Although this may not be the distance, area or type of school that you are looking for I thought that I'd share my thoughts. 