As has been suggested, a detailer rather than body shop will be your friend here. We both achieve very similar results at face value, but have significantly differing ways of achieving them.
A detailer will look to decontaminate in the gentlest methods / products possible. A bodyshop *tend to opt for a rotary buffing session which *can remove the contaminates attached to the surface but subsequently introduce new swirls and marring to the paint work. In the immediate it all looks good. Give it 4 weeks and the results are somewhat different once the fillers in their compounds have faded and washed out.
Ive completely decontaminated a white TT that had similar air born contaminates from a building site. It will be possible to remove - given the right person with the right approach.
Drop me a line if you wish any more thoughts or advice.
