The SAAB option looks interesting, but since any such fictional programme would be run on a short string, I cannot see any "Partner willing to invest in UK construction so such cost would have to be carried by the programme greatly increasing the cost, especially for such a small order. The only real money available would be as mentioned the funding for the T-31e and I cannot see that covering the cost of expanding Barrow, training personnel, amending any design, as we surely will and then actually building 3 to 4 state of the art SSKs for the available £1,25Bn. Oh and don't forget all the infrastructure to be built a Devonport to support them.
This for me make the programme totally non-viable. The only way we could possibly afford these boats would be for them to be built By the actual manufacture in their existing yards, with maybe a small amount of fitting out in the UK. If we were planning to build 8 to 12 of these then things might swing the other way, and more so if in future we look to a conventional design to replace the Astutes, but that would be 30 to 40 years away, which again points to what would the expanded Barrow do in the mean time? Well like always, let staff go and at best mothball the facility, at worst dismantle it.
Like with all naval ship building gin this country, for it to survive and provide value for money to the taxpayer, we need a steady stream of orders going to 2 or 3 shipyards. The MoD has a hard enough battle on its hand to retain the size of the fleet without the costs of new ships making at least 1 for 1 replacements possible.