Just a thought from left field, I have been pushing a personal barrow of the RAN procuring three to five Hyuga type DDHs, either instead of some frigates or possibly in addition to, could the same be a possibility for the RN?
My RAN concept is evolved from the RN suggestion that Australia delay acquisition of their planned missile destroyers as the proposed RN Escort Cruiser seemed a far better fit for the RANs needs than any then available options, MOTS or modified Charles F Adams class DDG, Brook class DEG, MOTs or modified County class DLG. Procurement of three such ships would even permit the retirement of the carrier Melbourne instead of converting her to an ASW helicopter carrier (plan was cancelled and new fixed wing aircraft were acquired instead). Anyway five escort cruisers were very nearly built for the RN in the late 60s. They were to have been in addition to the three CVAs, each leading an ASW or escort group. To help fund them the last pair of DLGs were cancelled, while the Tiger class cruisers were converted to helicopter cruisers to provide an interim capability. In the end the CVAs were cancelled and the RN looked to a class of six larger "Through Deck Cruisers" to fill the gap (with only three actually being ordered).
My thinking is why can't the RN take another look at the Escort Cruiser, or even the Japanese DDH concepts to supplement or augment the new carriers? Something smaller that can easily be adapted to ASW, sea control, LPH, HADR, MCM roles, employed where a single frigate or destroyer, let alone an OPV, would be inadequate, but a carrier and it's escorts inappropriate (because it either overkill or too great a risk).
Build the original eight Type 26 ASW frigates with their TAS etc. but seriously look at three to five new Escort Cruisers instead of the five GP frigates. You could still use Artisan and Sea Ceptor on these ships but instead of a medium calibre gun, harpoon and torpedo tubes, they would have a flat deck and hanger for several Merlin and Wildcat, as well as possibly Crowsnest and maybe being able to cross deck, or even operate a small number of F-35B. Japan operates a MCM version of the EH101, why not a Merlin variant? Deck spots for Chinook, Osprey, why not Apache and UAV/UCAVs as well?
Just a rehash of an old idea, after all steel is cheap and air is free while these ships would make use of existing assets concurrently while relying on just the two QECs (sometimes only one) that may not be possible.