Whenever I hear someone talk about finding his or her unique selling point, the hair on the back of my neck stands on end. If you are in complex B2B selling, you should not waste your time looking for a unique selling point.
Instead, you need to know your value proposition, which includes all the unique things you do.
As you build your approach to a particular potential buyer, you will use the unique thing you do that appeals to that particular buyer to build your value proposition. For another buyer, a different unique offering may be more suitable; you would then build your value proposition for this new buyer with a different unique offering.