On both aircraft, I'd go for two next to each other between 3 & 6K or, on the A346 only, two next to each other between 9 & 12A.
Because they face a wall rather than the seat opposite, they feel a bit more private. Unfortunately the layout of the UC cabin means none of the seats are ideal for couples who want to chat.
my favourite is 4&5k as they face a wall and are equal distance from the bar and toilet. but as gumshoe said none of the seats are ideal for chatting although you could sit at her ottoman. we always do at dinner and thats quite cool.