What's this bit for ( pictured).  Is it for the auto lights - which my car doesn't have.  

Thanks 

That is for you auto wipers, which aren't all that good to be honest.

Ok thank you. 

Should do the auto lights as well with the addition of the correct switch. 

That's the RLS (Rain/Light sensor). My car was equipped with it but with no auto lights switch. it was only a matter of installing an auto switch to get the auto lights.

Many thanks, that's the answer I was hoping to get. Now off to order the correct switch.  

Before you do, pull the old one out and check that all 10 wires exist in the plug. If you only have 9 then you can't use the auto on the switch and you will need to draw the 10th wire.