Type 31, Type 32, and Britain's available shipyards

Would additional Type 31s and Type 32 variants based on the same hull cost less than developing an entirely new platform?

Yes. The Type 31 baseline is judged to fit both the cost argument for follow-on batches and the expected availability of British shipyards.

The expectation is that Type 32 will become a second batch of Type 31, because Britain's available shipyards constrain the choice of platform. In this assessment, the Type 26 production and finishing facilities are being prepared to move on to the much larger Type 83. Harland and Wolff's support-ship workload leaves Cammell Laird as the likely yard for the next amphibious ships. The dock capable of maintaining the Queen Elizabeth-class carriers must remain available because alternative dry docks have not been upgraded. The Type 31 yard is considered suitable for follow-on ships in the same size category. Extra space in the Type 26 facilities is offered as a clue to the anticipated Type 83 dimensions.