The price for mixing a track sounds suspiciously low for a decent job. It takes 4 to 7 hours to mix a track properly so don't understand how it could be done for 65 euro. Don't see on the website anything that inspires confidence in terms of established credits (would "The BBC" really use such a studio and supply a testimonial?)
The price for mastering an album is at least half the price of cheap established mastering engineers with verifiable discography.
The engineer may be good and working at a loss to attract new clients, but if I were you I would be weary to commit to more than a song in case it is a total waste of time & money.
When something looks too good to be true, it usually is...