.....I believe they plan to place some on existing nuclear sites, thus speeding up planning permission.Some may be small RR plants.
As far as I can find, there are no example RR SMR plants actually existing, various news articles, quote from May 2021
https://www.rolls-royce.com/media/press-releases/2021/17-05-2021-more-power-and-updated-design-revealed-as-nuclear-power-team-targets-first-place.aspx"It has also announced it is aiming to be the first design
to be assessed by regulators in the second half of 2021 in the newly-opened assessment window, which will keep it on track to
complete its first unit in the early 2030s and build up to 10 by 2035."
(my bold text).
They use phrases like "off the shelf components". My guess is that will be bricks, everything else concerned with military/aerospace/nuclear/medical industries is specialised and costs £££££ in my experience.
Now I have great respect for RR, but I also recognise press release content when I see it. Sure they'll do it, but on time and to cost? I won't bet my pension on it and I wouldn't base a strategic energy plan on it.
When in industry I learnt the one thing you don't do is commit to a hard plan with a specified job#1 date when you include unproven technology. It always bites you in the bum. That was one of the principles I found typical of the Japanese suppliers, they did all the R&D up front and when they knew all the answers they would commit it to production, and not before.