Can I have a bullhorn lip lift and septoplasty?

You can definitely combine the septoplasty with a lip lift, but you have to make sure that your septoplasty surgeon has the proper skills to do a  good lip lift. Lip lift is a newer procedure that many surgeons aren't familiar with.  Make sure you ask to see before and after pictures. I had a patient about three years ago who came from Australia for a lip lift by me. She had had a facelift by an internationally known plastic surgeon who was honest enough telling her that he had no experience with the lip lift procedure.

Yes, they can be done at the same time. Several studies have now shown no increased risk when combining the procedures as long as they are done with care and proper technique. Best of luck.

Short answer, yes! 
There have been published case series about combining open septorhinoplasty with bullhorn lip lifts and it has been shown to be safe for healing. If you are only having a septoplasty then likely the incision will be even further away from the  lip lift incision and thus even safer. I would not hesitate to offer this treatment combination. Best of luck. 
Gary Linkov, MD