average commercial airline pilot wageWatch
As nice as £140k would be as a starting salary, even the highest-paid pilots in most airlines wouldn't get very close to this. Starting salaries vary considerably, depending on airline and aircraft type. It may start at £20k or so with some airlines, but nearer £35k with others.
Training will cost an enormous amount - even those airlines that claim to offer some sort of 'sponsorship' in the UK will require you to deposit a cash bond for +/- £60k, and will pay you a reduced salary for the first X years (during which time, you are not allowed to leave, unless you want to get the bill for additional training costs). Basically, unless you have a lottery win, very rich parents or are prepared to get into enormous debt, getting into flying is very difficult.
Stub: Probably not a good idea to let any First Officer hear you referring to them as "the guy sitting next to the pilot"! Both fly the aircraft (the FO doesn't just assist) and both are pilots. The Captain will have more flying hours experience, overall responsibility for the safety of the aircraft and passengers, and in some scenarious, extra responsibilities in training, etc.
no1topman: Flight engineers generally don't 'exist' anymore. Modern aircraft only require two members of flight crew. I can't really think of any UK airlines that still operate aircraft requiring a FE.
Although I am not a pilot myself, I am planning to undergo training in the near future and know a number of pilots with different operators, so will try my best to answer any questions!