Building Regulations for kitchen diner with staircase and removal of side door

CornyCob

We're looking to take out the load bearing wall between our kitchen and dining room, block up the external side door in the kitchen and add a new internal door into the garage (as per plans below). I understand we will need buildings regs approval for the works but was just wondering if there's anything beyond the expected that may be a stumbling block? Particularly with respect to fire regs as the stairs would now be in the kitchen diner (it's a 2 storey detached house) and whether blocking up the side door would impact this? The staircase is currently not enclosed but is open within the dining room and there are double patio doors into the garden at the rear of the dining room.

I understand we will need the standard structural calcs for the RSJ and a self closing FD30 door into the garage with a 100mm step but is there anything else I'm missing?

Thanks in advance.