Hi, I live on Portland, and happy that someone is modelling it.
My question is why Portland? Yes it is if it stayed past 1965 but i wouldn't imagine a oil depot and diesel depot on this small island, since at weymouth its good enough yard. Also, the layout doesn't show the continuation to Easton, if i am thinking this right that this version or portland is based where the old one used to be next to victoria square. It seems like its completely your idea and just have used the name Portland for the layout.
Im not trying to be rude, please don't read it that way, as i said im happy that someone is modelling it. But in places it confuses me.