I'm not really interested but I'm guessing you're not getting any replies as you don't really include any info that a serious affiliate is going to need to be able to make informed choices here.
£20 commission on an iPad would be brilliant. £20 on a £10,000 tv would be absolute garbage.
And no details whatsoever of interest. If you're sticking it to low end consumers with 40% apr then I'd want a hell of a lot more than £20 as at that level and even a £2000 tv over 3 years you're absolutely raking it it.