One of the tricks to really selling a composite image is to make the colours match from the foreground to the background. I have been following a great British photographer, #Glyn Dewis , he has produced a great tutorial for a very quick and easy trick to match the colours and sell the fake, you can find it HERE.
This was the out of camera portrait i used, i made some colour corrections in lightroom for skin tones etc took it into photoshop for a few more tone and contrast adjustments and then removed myself from the background using the quick selection tool and refine edge to finalize the selection and output it to a layer with a layer mask.
I had taken this shot of St Pauls a little while ago so with this image open in photoshop i then selected the image of me with the layer mask from the portrait and using the move tool i draged it into this document, scaled and re positioned me in the bottom right. After doing this i made some adjustments to the layer mask , but the colours just looked wrong. I then followed the tutorial as described by #Glyn Dewis to finish the image off.
I still have a lot to learn about compositing images but its a subject i am enjoying.