Extending raised Patio

Hello, we have been going round in circles deciding what to do with our front porch area and I think we have finally finally decided what do to.

We have a raised patio outside our font door which needs redoing. It has a concrete slab underneath

Im thinking to edge the slab with sleepers, we also want to extend it slightly to the side as a place for storage, so will use sleepers to frame the area.



For the existing patio area im thinking I need to remove the current slabs, then fill in with MOT 1? to bring it up to the level of current slabs / to the top of the sleepers - the current slabs sit on big dabs of mortar and sand and soil - then will lay new patio slabs on top on a full bed of mortar.

The small extension in front of the fence is about 306cm from ground to top of current slabs. After digging out the grass is ok to backfill the whole thing with MOT 1 as well, and then mortar bed and slabs or should I use something else to backfill the bigger area. Could I reuse the old patio slabs to build up the level?

Thanks
M