Hi Camara! If the project is right for you and you get on with your supervisor, I would absolutely take the offer. Funded PhDs (I assume this one comes with funding?!) are getting more and more hard to come by, and there is nothing to say that you will find an ideal PhD with an ideal supervisor anywhere else if you leave it for a year or two. I have done my BSc, MSc and PhD at the same uni, and it is actually very common to have the same supervisor for your masters and PhD, or at least it is where I am studying. Good luck with it all!