Stretching the definition of 'London' slightly:
All joking aside we decided not to try to filter out jobs in other countries because knowing where a startup is hiring might actually be interesting or useful. We're hoping to improve how the site handles different locations soon.
Unless Ocado have moved their development operations since last time I checked, I believe the job is actually located in Hatfield which is not even in the M25
Whilst this might be a generalisation, most workers in London don't own a car, so public transportation is obviously a key deciding factor when taking into consideration the commute.