It was offered for the S2 by Hermes, either alone or as part of a package. The Hermes Europa conversions were tested by Car and Motor magazines, both tests reproduced in the Brooklands series of books. You can just about make it out in the mono photos, I'd scan the article but it would probably exceed the limit on attachments and to be honest, Brooklands books aren't the greatest quality.
Motor said the aerofoil cost £7.75 fitted as part of a £550 conversion and speculated that it took about 12mph off the top speed with the extra drag.
Car said the aerofoil improved stability at speed but weren't impressed by the other suspension mods, specifically the damper settings which were apparently set too soft. And Motor said they were too firm......
Brian