For a house in the interior of Sunningdale the honest recommendation is modest. Neighbours on every side, occupied streets, ordinary passing activity — the informal cover that protects a normal suburb is fully present, and the sensible spend is on making sure the developer hardware is in good working order rather than on replacing it with something heavier.
For a house on the outer line it is a different conversation entirely. There is no neighbour and no street on the veld side, no lighting, and no reason for anybody to be there — which means anyone who is has both time and privacy. That boundary and the doors nearest it warrant genuine attack resistance rather than the developer's standard, and it is a small number of specific items rather than a whole-house programme.
The one thing both halves share is the age question. This is young housing, and in a great many properties the cylinders that came through the construction period are still in the doors. That has nothing to do with which street you are on and everything to do with how recently the suburb was built, and it is the cheapest thing on anybody's list to put right.