Hmmmm .......... new-builds are always a tricky beast to work out remotely, as it is down to the planner as to where he can find a suitable amount of available 'spare pairs' with which to feed the new development.
I've looked at our 'Prints' and can find no rhyme nor reason as to why PCP46 (Walthamstow) would be where he planned your development from, incredibly unrealistic.
The thing is, (as you seem aware), one half of your road (the odd numbers) are fed from Higham Park, and the even numbered dwellings are fed from Walthamstow.
There is a cable showing on our 'Prints' feeding long standing premises such as the Library which is right next to your new-build, and this appears to be fed from SCP41/1 (Secondary Connection Point), which in turn is linked to PCP41 (Primary Connection Point) situated on Waverley Rd/Wood St. It is at the PCP where the DSLAM (FTTC product) is situated, and is approx. 400mtrs from your new-build.
My own opinion is that it would have been the easiest and more cost-effective method to have fed the new-builds from PCP46 Higham Park, as the capacity for the extra circuits required would be easy for the planner to source, but as the two Exchange boundaries (HP and Walthamstow) are split right down the centre of Forest Rd, I wouldn't know if this would be an option ??