what is a realisitic figure to be earning in the UK as a B1/2 LAE?
A lot more than a SNCO or WO in the RAF!!
You're looking at a starting salary of £40k for a B1 or B2 LAE with one type rating at your typical UK Airline/MRO. Extra tyes attract additional approval payments and can push this figure up significantly. A LAE with multiple types will pull in somewhere in the region of £50-60k. Overtime is extra.
Third partly MRO's don't tend to pay so well. An unlicensed line mechanic at my place of work will earn the same as a certifier at Alber Ratman's employer.