The answer to your question is clearly set out on the Wilsons website under its admissions criteria. To save you the bother of looking it up, I have copied it here:
Quote:
Where the number of eligible candidates for admission exceeds the number of places available, places are offered to boys in the order set out below:
Looked After Children or Previously Looked After Children** by rank order of standardised score in the entrance tests;
10 places for boys eligible to receive Free School Meals*** by rank order of standardised score in the entrance tests;
Remaining places including any unallocated places under criterion 2 will be allocated to boys according to their position in the rank order of standardised score in the entrance tests.
Where candidates have the same rank order and where the admission of all would exceed the number of places available, places will be allocated in the following order:
firstly to candidates whose permanent home address**** is within the London Borough of Sutton in the order of the distance of their home address (with those living closest being given priority) measured in a straight line from the main front door of Wilson’s School; secondly to those candidates who live elsewhere in the order of the distance of their home address (with those living closest being given priority) measured in a straight line from the main front door of Wilson's School. In the event that candidates have the same rank order and cannot be separated by distance the applications will be determined by a random ballot supervised by an independent person.
Wilson's PAN is 180 - therefore almost all the places will be determined by score, not by address.
If it sounds like I'm being snippy, it's because I notice you've posted a similar question about Reading (Reading! You're not planning on your DS travelling there from TW are you?) without seemingly understanding your chances of getting a place at that school. Your son has done all the hard work in sitting these tests, yet you don't seem to have as much as glanced at the admissions criteria.