Sidestick lifestyle issues include things like rostering, the ability to plan days off in the future, leave allocation, overtime working agreements, and a host of other factors that individually are minor, but together can have a large effect on lifestyle. Improvements can always be made, and the goalposts are constantly moving even in the best of companies. And pay talks are never just about pay...!
You are confusing length-of-service increments with annual RPI uplifts. There is no element of RPI associated with LOS increments. The LOS incrementation is based on whatever your salary is on the anniversary of your entry to the company. RPI and other negotiated salary increases happen on an agreed date for all employees in a given group. The combination of increment and negotiated increase will be considerably more than the figures you mention. The details of the last BALPA-negotiated Virgin pay deal have been discussed and published here before; suffice to say the increase over the last three years has been very substantial. We don't earn as much as BA pilots do, particularly in the later years, but we don't work as hard either!
Allowances are based on an agreed daily subsistence rate for each hotel. This figure is agreed also with the Inland Revenue as adequate to provide a reasonable standard of living consistent with our expectations and the facilities on offer (themselves subject to union/company negotiation), and not as an income supplement, and is thus tax free as of earlier this year. The total allownces received in a year is highly dependent on where you go and how often you go there! One person could get £4000, another £10,000. Most will get something in between.