Hi

I changed the nearside main beam headlight this morning after it failed,

Its much easier to change than many cars.

When I put the headlight unit back in it does not appear to seat as snug as before.

There is now an obvious gap between the top of the unit and the front edge of the wing.

Does anyone have any ideas what's caused this. 

Thanks

Take it back out and spray the slider faces with silicon spray (back to black etc) then put it back in. if it doesn't line up properly make sure the release lever is pulled back properly and try again.