In my experience UKSF have moved to these style rails and PTS stocks. Can have whatever optic the individual operator feels happy with, but generally they have a close range optic with a flip to side or twist off magnifier. Also I think they'd put attachments on that are relative to the mission. The key is a good paint job, make it look more like SF style.
I have a JPC, spent about £50 on it and it seems decent. Also SF use whatever plate carrier works for the individual operator, there's a serious mix of kit. So don't be afraid to make it your own.
Happy building!
