King size mattress (Runwell SS11)

King size mattress. Memory foam and springs. Approx 3.5 years old but in very good condition. It’s always had a mattress protector on top and my eldest daughter had it her bedroom while she was in university - so it obviously wasn’t used while she’s away. She’s now living with her boyfriend and my youngest daughter has taken the bigger bedroom. But she finds the mattress to be too soft so I’ve purchased a firmer one in the Black Friday sales. The old mattress will fold as it’s memory foam based and it’ll spring back again. It’s on my landing at the mo unfolded and in the way so I’d like it to go asap otherwise it’ll have to go to the tip which will be a shame as there’s nothing wrong with it.