Obviously nobody is officially 'qualified' by the CAA yet to deliver on-aircraft UPRT - in fact, the CAA haven't even approved any FCL.915(e) UPRT FI programmes yet, even though FCL.745.A becomes mandatory less than 2 weeks from now.
For me, delivery of on-aircraft UPRT is probably one of the most challenging aspects of being an FI (although I'm obviously biased!), and the pay rates should reflect that.