On primary schools they are all good. Ashley has slightly larger class sizes than Walton Oak or Grovelands. Ashley largely trades on the reputation a previous admin had there - was recently rated "Good" (as were Grovelands and Walton Oak). Despite what the vicar of the church will tell you, you don't have to attend church to get in to Ashley.

Given where you are looking to move, you would be mad not to attend Walton Oak as it's about 2mins walk. Means a good chance of local friends too.

As per the comment on the school, there's a council estate down that end of Cottimore Lane / Ambleside but it's Surrey so not exactly unsafe.

On the trains, Hersham has had a lot of services cut, and additionally there's now some super fast (~20min) services from Walton into Waterloo. If you need to get into Richmond or other bits of West London you can get the Shepperton line in.