+1 waiting for the GamersGate version.
I tried buying it from their website, but their payment provider blows (currently abroad so Paypal payment was blocked for some reason and the credit card authorization also didn't work).
Well I decided to try and purchase from the Graviteam site, man what a rough experience. I too received payment failed messages but kept clicking continue and ended up with an order number and download link. If the link had not been posted here there is no way I would have continued. The whole process was very dodgy and did not act like a legitimate site.
Got the 222MB file (sa_basra86_dlc_int) and added the extension manually (sa_basra86_dlc_int.gt2extension) and it installed OK. I put it in the list above the last patch.
Please get that payment method sorted out. A lot of people may not take the risks I took and continue through error messages.
But all's well that ends well.
Regards MarkL