"Well, I only ever get the frozen ones from ASDA and I like them with normal bread, not buns"
that, my friend, is more commonly know as a "welfare burger"

"Well, I only ever get the frozen ones from ASDA and I like them with normal bread, not buns"
Kill them, kill them all.
He sounds like a total self-gratification artist from what you say here, but does he have any redeeming features? I presume there must be some reason why you invite him. If not, why bother inviting him at all?
I agree with this. Life's too short to befriend peanuts. Next time phone him up and tell him you're having a barbecue and he can f**k right off.
It sounds like the guy is on the autistic spectrum, both the fussiness/preference for bland processed food and the inability to deal with it diplomatically suggest that.