CPA business models for competitions / prize sites

Does anyone have any research on how these sites operate? Especially interested in UK competitions sites which seem to have very little information.

I'm guessing there are 2 types; CPA affiliates & lead generation...

CPA affiliates - do any of the affiliate providers give feeds (rather than having to manually add/rotate offers)?

Lead Generation - cannot find much info on this regarding rates etc...I guess it is a little like becoming an affiliate network

If you have any info I'd appreciate it

i'm interested in soft cpa too