As with any medical condition there is a matter of degree, see CAP562 leaflet 15-6 (supersedes AWN47). There are restrictions on holding driving licences as well so some latitude may be allowable. The CAA could probably advise on this if you email them at the engineers licensing dept in Gatwick. IME they're a bit slow but they will get back to you.
CAP 562: Civil Aircraft Airworthiness Information and Procedures (CAAIP) | Publications | CAA
As regards earnings this varies a great deal according to employer and skill. £20-30K at a guess. As you're asking about B2 I presume you're interested in avionics/electronics. Due to the specialised nature of modern avionics very few airlines have their own avionics workshops and most of the "open box" work takes place back in industry. Have a word with Avionicare and Oakenhurst to see if they could offer you work experience or apprenticeship. Otherwise people like Rockwell Collins and Honeywell (not in your area though) may be able to offer advice of where they recruit from.