Ive quickly counted the number of South African players and the total number of non-English players by each club. This is just taken off Wikipedia, so take with a pinch of salt, but I didn’t notice any glaring errors:
Exeter 2/18
Sarries 2/11
Bath 1/9
Northampton 4/14
Sale 9/15
Gloucester 6/17
Bristol 1/19
Worcester 8/28
Wasps 3/14
Irish 3/28
Leicester 3/20
Quins 3/17

At a glance, I would say we don’t have to worry about becoming Known as SA Harlequins, we are very much in line with the bulk of the league. Sale, Gloucester and Worcester lead the way in South African players. Interestingly, Worcester and Irish have significantly more non-English players than the rest, probably because it’s cheaper. At the other end, big budget teams Sarries and Bath have the fewest non-English players as they don’t need to pinch the pennies.

I had a quick look at the Sarries squad from 2010 as a comparison on the South African numbers, and they had 8 full blown South Africans in their squad that season and a further 5 born in South Africa but declared for another nation.