The 45K is a complete red herring. As a TRE on a UK contract my P60 was @£120K, most LTCs and line Capts are nudging £90 to £100K and if you work a few days off you can boost your pay significantly.
Remember FR is a productivity based airline ie low basic but high rewards for being at work so high sector pay.
There is one big advantage is that you only pay higher rate tax on a small basic.
Disadvantage is my Final Salary pension which I am lucky to be in (closed in 2000) is based only on my salary not my overall earnings.
Other disadvantage is no fly = very little pay. However FR know this so try to ensure flying hours are kept high. Other wise every would leave.
Can only speak for myself but FR has over 2500 pilots. We cant all be deluded and most wouldnt be here if the money was only £45K. I wouldnt am worth a hell of alot more than that....