The benefit to the UK of the order is primarily in equipment supply. AIUI, the propulsion system pretty much as supplied to UK T26 will go in the Hunters so good news for RR.
There will also be a secondary benefit in that a significant amount of detail design work will need doing to reflect the significant changes in combat system equipment and other items, which will in all probability be done in the UK. That's paid work for a hundred bods or more for a couple of years that would otherwise mean firing them (they don't subsequently tend to come back to the industry, so you have to rebuild that skillset from a lower base) or would in someway land on UK contract overheads or make contracts BAE were bidding in the UK (even) more expensive.
What it won't stop is the SNP whinging about not getting their frigate factory at Scotstoun......