I watch a few British panel shows (as an American) and I am under the impression that Nandos (probably spelled wrong) is a Curry restaurant, and curry restaurants are a fairly common thing in Britannia. I honestly couldn't tell you what curry is, I thought it was a spice but I see references to it on panel shows as being some dip thingy, with giant cracker thingies with a name I am too embarrassed to even attempt to spell (pop-a-nums?). Cheeky is a term I think I understand in context but feel too ignorant to attempt to define here.
With all that in mind, my assumption is that having a cheeky nandos, in the context of the OP's image thingy is that people were contemplating getting some form of curry food, and then one person suggested, in some sly fashion, to visit Nandos to satisfy their craving.
How horribly incorrect am I? Regardless, having never heard of this cheeky nandos thing before reading the OP, I am instantly fascinated, especially by the sentences presented in the picture (Banterbury is just funny).