ihk you can apply for fiance visa, as the fiance of an EEA national which is covered under rule 290A of the Immigration rules, rather than the EEA regulations or the directive, as EU law does not cover fiance.
If however you can satisfy the Entry clearance officer you have been in a durable relationship, then you may be qualified for an EEA family permit, following an extensive examination of your personal circumstance.
The Problem with applying under Rule
290A, is the fact that, you could be refused on
320(18 ), or the refusal under that rule could still stand, as the concession for that application is made on national rules grounds as opposed to the EEA regulations.
As you are seeking to enter on a fiance visa, it will be safe to say you are intending on getting married, if that is the case, then you best option is to probably get married in SA, as the hurdle you will face to get a fiance visa, will be really stiff.