According to the berlitz guide they have 4 wheelchair accessible cabins on this ship but it doesnt give any information on the specific facilities in them. Suggest you either speak to Thomson or your Travel Agen.
Having been on board the Celebration last summer, which is the sister ship to the Spirit. The cabin layouts are exactly the same.
I shared a wheelchair accessible cabin with my disabled brother, which are located on deck seven and just below the bridge of the ship.
The cabins are a generous size and there is no need to worry, everything is wheelchair user friendly.
The shower includes a drop down seat and the sink is accessible for wheelchair users.
The drawer units are wheelchair user friendly also, but they will need a hand if they need to hang anything in any of the double wardrobes, as the hanging rails are a little bit to high for them.
There is no need to worry about access to these cabins, as the doors are a little bit wider than the other cabins.
My brother really enjoyed his time on the cruise and had no trouble getting around the ship, as there are ramps to the majority of doors and the lifts are accessible for wheelchairs.