I'm sure you can't answer this, but are you paying him anywhere near $100,000 (£66,000)? In my experience that's about twice what a bog standard junior dev outside of finance, Facebook, Palantir, Facebook etc gets in London.
Which rather puts the £8k fees in an unflattering perspective, but there you go.
if its is so it's time to dust of my interesting bits of my job using ML to optimise ppc acountmanageent