Commercial Element is nearly always a vacant value. Unless you have a blue chip company on a long lease when we can sometimes achieve a market value.
Residential Element will be valued using similar comparable properties in the area. Remember properties above commercial are usually less desirable.
If you have an HMO as part of the residential part, you may be able to achieve an uplift on the bricks and mortar with a yield-based or hybrid valuation. This is where you can benefit!
You will either end up with an aggregate value (the sum of the individual parts) or a block value for the building, where around 10% is deducted from the aggregate value.
Which figure the lender uses will be up to the valuer and their comments. Can the property be broken up and sold individually? And would there be sufficient demand to do this in 12 months?