Ok so I am in same situation and yes I think you will have to withdraw application but they only gave me an update a month later. Meanwhile I thought my passport was being processed which was not helpful. I have cancelled 3 flights and due to go out on Sunday but that will probably be cancelled as well. No one answers the phone unless you are relentless. I am currently on hold for 2 hours 15 minutes.
I submitted both passports after requested name change and original marriage certificate. They said they won’t update my UK until I get the other one sorted first. I asked them how can I do that as you have my original marriage certificate…zero understanding. I wrote a letter registered post immediately cancelling application, that was over 2 weeks ago. All they need to do is send back everything as my UK one is still valid but they seem to be having an issue doing so. Total crap service, no customer service and you cannot get through to anyone so you are just a hostage to their poor system. Unfortunately you will just have to wait. Just a tip I was told the UK passport office will not issue a new passport in a different name to your overseas one under any circumstances. I would cancel the current application and ask docs to be returned. Good luck though I’ve been waiting for weeks. Its so stressful I missed a funeral and all of my family are there but no point appealing on compassion grounds because no one cares.