Thanks - Hello! I didn't realise I hadn't posted before, been lurking on here for years. This forum is a very useful resource!
The changes apply to both First and Standard; new cushions and arms throughout. The original-vs-enhanced images on the website are of the First Class seat. The photos of the mock-up show where new foam has been added to improve comfort and appearance. The studio renders below that show First and Standard side-by-side production design, which have been on display at various EMR stations over the last year.
Seat comfort is such a personal matter with lots of opinions and, rightly, some negative expectations based on recent new seats. The whole project set out with comfort at the centre of the seat and within the various requirements (including but not limited to fire, crash, weight, cost, durability, cleaning and maintenance) I think it'll be the best new seat on a UK train. I'll be reading everyone's reactions with interest!