Fairlawn catchment didn't used to be so small
So a large proportion of places will have gone to siblings of children already at Fairlawn. The best way to get your child into the school of your choice is to marry somebody with a child already at that school, so that your child has the right sibblings. Not that I would want to encourage wife swapping on the posh estate, but that's 'social mobility' for you!
jeh's last point should add another £20k to the value of houses within 384m of Fairlawn
Fortunately, as is pointed out in so many threads about schools, Forest Hill has a good number of excellent primary schools, even with their buldge classes.