City of Westminster sits in the Greater London and operates a Gateway 3 Building Safety regime — meaning intensive Gateway 3 sign-off and HRB oversight for higher-risk schemes.
The Scapely cost model puts the typical build cost in City of Westminster at £3400/sqm for a standard residential conversion or new-build, before professional fees and contingency. Use this as a rule-of-thumb when stress-testing a deal — Scapely Pro produces a per-property estimate from CIL, footprint and access constraints.
Article 4 directions are active in City of Westminster. Permitted development rights have been removed in defined zones, which means HMO conversions, office-to-resi schemes and other PD plays require a full planning application. Always check the council's Article 4 map before committing.