I think the UK PLC needs to take a very large 'chill-pill' on price.
While £250m is a fair lump, UK RN lives by the motto "Champagne Lifestyle on Lemonade wages". I'm pretty sure that everyone taking part has stated that steel is cheap & air is free, but IF UK RN wants to get the ship they're asking for, you'll need to do better than £250m.
T26 has so much complexity & overheads built into it from the get-go. The fact that the initial design phase of the project has been running since about 2010, with contracts only being placed in 2016 (after a 'slow-down' in the design at the customers request), these are all things that add to the overall costs. I'm sure that the difference in cost between batch 1 & batch 2 will be significantly lower, as the gremlins are all worked out, but I still foresee them being circa double the costs quoted in the 1st line of this paragraph !
UK RN & the Admiralty as a whole has the problem that they only have so many hulls, so many bodies & so much funds to do everything. T31 is supposed to be a GP Frigate, NOT a T26, so having a big mission bay, or using the T26 hull form may have made sense if we were building the x2 ship designs alternately on the same 'production line', but with UK PLC stating that they want the first ship in the water by 2023 (the same time as T26), they are on a hiding to nothing, especially if they are being built in sections & assembled elsewhere, so not to be under the control of BAE.
Other Naval manufacturers across the globe usually sit down with the client navy, discuss key points about equipment / hull-form, etc. that the sovereign state wants, agree a fixed price & then accept the ship several years later once it's been completed & tested. ANY changes are deemed as extras & have to be paid for accordingly, over & above the original spec. price.
UK manufacturers have always had to deal with a navy that is sat on their shoulder, making changes constantly & then starts blaming the Industry for the delays (Carrier Alliance & the Cats & Traps / E-MALS fiasco being point of fact).
The fact that T31 is supposed to be a GP frigate, should mean that it is close to, but not exactly a single-role piece of equipment. GP (General Purpose), doesn't mean chop/change/adapt/fit new modular equipment every 2 mins, but that the ship is a tool box that contains all the equipment needed to do that task (whatever the task is), with little alternation.
As for size / costs, T26 is almost as large as T45 probably somewhere in the 5 - 7000 GRT weight range, T31 is expected to probably be no more than 4000 GRT. & while it may look to the layman that a stripped T26 is a T31, the reality is that we're not comparing apples with apples, as the hull design / equipment spec / range & capability are very different.
Finally, there's the legislative & regulatory aspects that UK PLC demands (which is often over & above what other countries agree with the supplier, or have in place). The demands to have certain fit & finish means that additional cost is built in, due to the numerous tests / trials & 'provenance' of the paper-trail that links back to specific specifications for equipment.
