Hello,
Does the residential part of the property have it's own access, or is entry via the commercial part of the property ?
Banks are more attracted to two seperate, stand alone entrances as it helps facilitate breaking the property up, in the event that a forced sale is required.
Furthermore, is the property on one title or two, if two then again it would be more attractive to a lender - infact in theory, you could have a homeloan on the residential title and seperately, a commercial loan on the commercial property.
If the title is all one at present, you may struggle to attract new lenders. Perhaps explore the possibility of splitting the title, to seperate the residential and commercial elements with the Banks and if they are favorably disposed to it, then explore the costs with a solicitor etc.