Don't Tell the Bride - series three Jonny and Ayca

It showed the groom packing Coast bags so I reckon that would be a good place to start - it didn't say what year it was filmed though so they're probably not current - it was definitely a July!

They looked like they came from a Coast inside a debenham,

I think the episode was an old series 3 repeat, so they are unlikely to be in the shops at the moment - i'd try an outlet centre such as Bicester villiage as that's the kind of place all their end of line stuff goes.