Single bed frame and mattress (RH12)

Frame is as pristine as the day it was delivered - still in the box - with slats to go on the bottom. I also have a good quality barely used single mattress (2 months' use tops, by an adult, so clean, and currently around £350 in the store). So long since I bought the frame, I can't remember which one it is, but the picture should give an idea. Dimensions on the box are 1878 x 207 x 72 cm. Got someone graduating to big bed, or need an occasional for visitors? You will have to collect - Fiesta not big enough!