Halifax mortgage rates

I have a mortgage offer from Halifax at 4.65% (5 year fix, 80% LTV), which was prior to BOE reduction. Havent agreed a completion date yet but estate agents said the seller was hoping mid-end of September. Does anyone know how long Halifax take to issue new rates? Other banks have done so (Natwest and others are offering 4.24%). Hoping Halifax release new rates in time before completion!!