What you seem to require isn’t ‘number porting’, that’s where , remaining at the same address , someone moves their phone number to a new provider…your requirement is more a house move , but maintaining service at the old address….a basic requirement is that the new address and your current ( residential ) address would need to be physically connected to the same exchange , if the addresses are sufficiently far apart ( distance wise ) then you could not take the number across exchange boundaries .
The other complications are that usually by taking a number somewhere else , it automatically ceases any other services on the line at the original address, so broadband may well be ceased at the residential address, plus if the new location is a business address, you may have the complication of residential to business transfer .
If you wanted to do this , and assuming both addresses are connected to the same exchange, you would probably have to renumber the residential line , that makes the number spare , then ensure that the now spare number is allocated to your business address…there would probably be some time while the number would simply be spare, and you would have ( IMHO ) have to get this done in a managed way , by speaking to someone who understands what you want and can manipulate the orders through the system.
TBH, if all you want is to be able to answer phone calls that would go to the residential address from the business address, you could just get a line installed at the business ( with any number ) and when leaving the residential address put the existing line onto divert to the number at the business , callers will be non the wiser , they call you, and get you , the only draw back is you pay for the diverted part of the call, this would work even if the addresses were off different exchanges
