Getting mattress up a very tight set of stairs

Our bedroom is in the loft and the stairs up to it are very tight, turning back on themselves with a limited width and headroom. We have tried getting a standard 20cm thick king size mattress from one of the bedrooms on the lower floor up but there is just not enough room.
We have looked at memory foam mattresses as I assumed that they could be rolled and almost bought a Tempur 21 until the salesman told us they couldn't be rolled or folded significantly.
Have now become aware of Ergoflex and Simba and they come rolled up, do we have any other options?