Cat tower (Tring)

I really need a Tall, great condition, cat tree/tower, it doesn't matter how intricate it is, my Rescue cat gets nervous with all the different Carers and medical proffessionals coming in and out of the house, and I can't put shelves up or afford a tall one for her to go on. Cats like to be up high especially when scared and she's hiding under my bed when she hears the door bless her! Does anyone have a tall one they don't need please, something their CST hasn't taken to or something? My cat Ella and I would be very very grateful! Tia