£10 an hour sounds about right for PPL level instruction from what I can remember. If you think things are bad in the UK you should see how instructors in the US get treated (at all licence/certificate delivery levels). I don't disagree that it is a poorly paid occupation in view of the risk and compared to the fees charged to the student.
Still baffles me why people still refer to it as FI(R) when this pre-dates JAR and it's been an FI(A) for as long as I've been flying near enough. Everyone is aware of the restrictions on a freshly printed FI(A) rating, don't see why people don't call it what it is.
Pre-JAA a 'restricted' FI(A) was referred to as an Assistant FI (AFI) and a Qualified FI (QFI) was one with privileges to teach applied instrument flying and other pre-requsite experience....and
Flight Instructors were known more romantically as Flying Instructors.