Can an extension to the period for reply be requested by the PM to respond to cl. 31.3?

Can an extension to the period for reply be requested by the PM to respond to cl. 31.3?

Can a Cl. 13.5 extension to a period for reply be requested where the contract gives a specific response timescale e.g. Cl. 31.3 gives a specific 2 week response whilst a Cl. 26.3 acceptance doesn’t give a specific period, meaning the period for reply in the CD part 1 applies. Are some response periods locked in?

Clause 13.5 only talks about the period of reply being extended, not a timescale already written within the contract. Therefore only something where the response time defaults to the period of reply (e.g. acceptance of design or a subcontractor), or under clause 62.5 the period to respond to a quotation can be extended. Everything else is “locked in” to use your language.

My bigger question is why should they ever need longer than two weeks to respond to a programme - especially when it is only another two weeks when the next one is due anyway. They should be able to respond to a programme within two weeks, especially if the programme is well presented with a thorough narrative attached explaining exactly what it shows and what has changed.