British Citizen returning to UK with EU passport

I am having to return home to UK with my EU passport. I am a dual national Finnish - British but have never had British passport as there has been no need for it, as I have an EU passport. I have been away for a few months and now need to return to home, UK. I didn't even think that this may be problematic until a friend asked how would that work with Brexit. I have been working remotely for a UK employer whilst in Finland but have now been given an ultinatum to return to the UK in 3 weeks latest. British passport will take longer so i will need to enter UK with my Finnish passport and my Naturalisation certificate. Will this suffice at Heathrow border control? Can any one help?

As long you can make it to UK border/Heathrow i.e. you have no restrictions to board a flight etc, you will be okay. You may face some delays before the UK immigration officials carry out some checks before releasing you.