I have carried out a search but am not clear on which Hexi Bolt to adjust for horizontal adjustment. My drivers side Xenon needs to move to the right a little.

You adjust both together by the same amount to adjust vertically, either one on its own to adjust horizontally. 2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed

I can adjust height no problem by turning the hex bolt however when i turn the other one to do left & right, nothing happens - just spins?

Have you tried the inner had screws? There should be 2 on each light

I can see two hex screws, an outer and inner. The Inner ones do not do anything - I can adjust vertical just not horizontal

If only one works then it should do horizontal, not vertical. Sounds like something might be amiss with your headlight. Have you tried taking it out and checking it for damage (and checking it's correctly located in the vehicle)? 2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed

Lights still won't adjust horizontally on Adaptive Headlamps - the hex screw just turns?

Sounds like someone has broken it in the past. You might try taking it to a garage and asking them to have a look at it. Hopefully it's not broken because the headlamp units aren't cheap... 2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed

So, I took another look at this last night and something clicked whilst turning the hex bolt and it started to feel a bit more purposeful and low and behold, the light started moving!

Thanks for the advice and I can now adjust to my hearts content!

 2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed