wow your MOT tester is pretty harsh, dirt attenuated ligh more than the cloudiness. Did he actually shw you the light intensity report and how much it failed by??
Either way (rant over) you can easily get the lenses off:
1; Purchase some RTV sealent/gasket maker. Either in Black or Grey (stock lights have grey on at present)
2: Remove the light from the vehicle and remove all bulbs and motors (height adjusters if you have them and they come out) and metal clips
3: Put the kitchen oven on to about 80-90 c (hopefully its electric / if gas just preheat to whatever gas mark this equated to), leave to pre-heat
4: put the light units into the oven for about 15-20 mins. (if gas oven turn off the gas before you put them in , dont want and fires, just leave then in warm oven
5: Remove a light (stagger putting them in an taking them out cause you can only part one at once) and use an old table knife of putty knife and work around the edge of the lens carefully parting the light and lens. If they are warm enough they should easily part
6: Polish whatever you want to your hearts content. work down sandpaper grits , then onto like G3 compound then fine polish. Do a search as others have said for best stuff
7: After removing all old sealer put a bead of new in and stick the lights back together and put on the metal clips. You may want to bead the outer edges too (i did just to be on safe side so no water gets in)
8: Put back in car, nice and bright
