Dividing existing property into 2

Hi All
I'm after some advice regards converting a property into 2, its currently owned by my parents and they are planning on moving so I am in a position to purchase it as a BTL
The property is freehold
It has some exterior access to the upper levels as it was previously a separate flat, due to its configuration it would need a partition wall up stairs and a bathroom downstairs

My questions are
1,Would I need planning permission ie instead of number 210 it would need to be 210a &210b ?
2,Would I need to enlist an architect and also get building control ?
3, Also I presume i would need to somehow separate the electrics so that each property is accountable for its own usage? Any suggestions would be appreciated, also same goes for the heating & hotwater, the combi boiler is in the upstairs property

Any information would be much appreciated
Thanks   

1. Yes you will to split (not needed to combine) But check with local planning
2. Building control yes. Architect optional (but you’d be foolhardy to try without) structural engineer likely needed to (depends on what you are doing).
3. Rather obvious but yes otherwise you won’t planning permission or building control permission

Thanks, I'm just on with finding an architect and i'll go from there