Hello Chris
I'm gonna assume you want to remove the front interior light yes? Ok, the lamp is TWO units, the actual lamp (frosted plastic peice) and its surround (the part with a small lip close to the windscreen that looks like you should pull on it!).
Only one part actually comes out! the frosted part ONLY.
You will need a small bladed screwdriver, insert the blade into the front of the frosted part (you will see a small slot on the side closest to the windscreen) and gently lever out. The surround is a mounting plate that the frosted plastic lamp slips into. To replace, just put one edge against the hole and push home.
A hint: take out the fuse first from your fuse box, sometimes parts of the lamp will catch the bare metal as you pull it out?replace the unit, and blow the fuse (then its no horn, fag lighter ect). Its all in your handbook.
As for the ariel - Im not sure, its something Ive not dealt with, try ford focus owners club on the web look for ffoc.
Have fun!
Graeme
March 2008