One has been opened but not used/touched. There is a Brewers nearby but wasn't sure how accomodating they would be with stuff bought online direct from F&B. It's one of those costs that has been consumed by the general reno costs, but I agree it's enough to think about trying.
Give them a call and ask - they might be happy to swap it for another colour which you could use elsewhere. Mind I'd just say you bought it there and lost the receipt. The railings colour is much nicer, good move!
Ah ok makes sense! Are they unopened? I returned paint to F&B and to Brewers and was pretty easy - at £30-50 a pop it felt worth it.