Depends on when it was installed. If after April 05, then it must be a condensing boiler, and you will require building regulation approval for it.
Typically, the CORGI installer would submit all the relvant paperwork and you would simply receive a certificate from CORGI.
As this is not the case, it is likely you would need building control to approve the installation, which requires a fee payable to them, an inspector to visit and sign the system off.
Speak to you local authority