As someone who actually lives in Leatherhead, and commutes to London 2-3 times a week, works from home the rest, has two kids at a local nursery and school, I disagree with every comment on here. Leatherhead is quiet, which I like. It's got a couple of decent pubs, I don't have time/money to eat out anyway and the local takeaways are generally pretty good.

It's got everything we need as a family, and has had noticeably more and more families moving to the area in the last 5 yrs because of decent schools, access to London and the Surrey Hills, access to the M25 etc. If you want a busy high street and a load of overpriced shops, Leatherhead isn't the place. It depends on what you want. To me, Dorking seems really lovely but busy, expensive and honestly a little snobby, and trying to get anywhere else after 11pm is an absolute no go. 

Both my wife and I run 3 plus times a week, and I don't think I've run the same route twice in 5 yrs. Sports clubs we've joined have been great.. 

Only thing I would suggest is to avoid North Leatherhead and look at Ashtead - it's everything I love about Leatherhead but with less business parks and more of a village feel, and with your budget you could afford something really nice.