Has anybody fitted STI spec rear lenses to their UK car? is it an easy DIY job or is it a bit more than unbolting the existing ones and replacing them with the STI ones.

Which STi are u talking abt? If it's the New Age then there's no need to change it - JDM & export spec share the same light clusters.

The classic shape!??!

I think there were many posts ages ago talked abt replacing JDM spec lights with export lights. One thing to bear in mind - the JDM spec cluster does not have space for the rear fog bulb to go into, unless u put the fog bulb into the reversing lamp (don't forget to paint the bulb red). Other than that, the main difference is of course the white indicators on the JDM cluster.

I should be replacing mine with clear/red Sti clusters.......just worried about the fog light thing and painting the bulb

it's easy.
done it to mine but you have to look out for the black sticky water sealant stuff.

take the screws off and take it off.