Thanks for replying Dan.
The second data set (the one I am overlaying the relationship on to) has 13,000 DBs. I am using projected data; however I did not run an OLS. I went straight to the GWR because of the Prediction Feature Class component allowing me to overlay a relationship onto a new area while the OLS did not allow me to do so; however, that was probably a mistake.
The parameters for the GWR I used were 1 explanatory variable, an adaptive kernel type, and an AICc bandwidth (no distances or weights were used).
I haven't heard of the MUAP issue so I will take a look at that paper, thank you for that knowledge.
From your comments, a solution may come from creating a proper OLS model then running that as a GWR and then creating a Prediction Feature Class using the best model