...to be honest, I have no clue how difficult it is to install these lights.

Get someone with an EPC (or go to a very friendly guy at the dealership) and look it up. Remove all filters at the EPC and look for the british or italian version of the W 124 (I think Honkong cars also get the additional indicator lights)

Concerning the vaccuum: The taping has nothing to do with the vaccuum. As mentioned above, right hand driven cars headlights have more light to the left of the road, left hand cars vice versa.

If a continental car enters Great Brittain, you have to take care not to blind the people there.

Kind regards
Eberhard