Actually, that Autoexpress article is a bit misleading. The SA prefix appears on dealers computer systems prefixing the chasssis but very few SA build cars were produced with SA on the chassis plate.
The WVW at the beginning is just part of the chassis filler - all chassis numbers for everything are seventeen digits. VW only need 10 so they chuck fillers in. All VW chassis nos. start WVWZZZ. Audis start WAUZZZ.
Barney, if you want to PM me your chassis or reg, I can find out for you tomorrow.
Very few GTIs were SA build though, mostly just SE and S models. Have a good look around under the bonnet, there are usually made in South Africa stickers hidden around (although some dealers actually peeled these off, i'm not joking)
VWmd