Could have spun cylinder then cables to immersions would have been fine.
Hard pipe to expansion vessel, but that's just me.
Expansion vessel straightened but that's purely aesthetic.
Isolation valve on hot from cylinder. I don't like to see that, especially as you have isolation on cold inlet.
Combination valve higher but that's just purely if it needs replacing at a later date
Plus the good old insulation.
Not a bad installation, but just like my school reports, could do better.
Do you have all the paperwork, building regs notifications etc, and seen the installers g3 qualification.