Sam,
There is of course the chance of going straight onto the 737,
with the industry in the position that it is (certainly within Europe) those chances are increased, however it is certainly not the norm to get onto the 737 at the first time of asking.
I have been lucky enough to get my first job on the 737, but I took the decision to pay for my own type rating. It was an educated gamble I would say, that happened to pay off, however without that extra training, I certainly do not think I would have landed my first job yet.
Flight training is a gamble, most of us do have large debts to manage so it is a decision not to be taken lightly, however if you are like me and flying is all you have ever wanted to do, go for it and donīt look back
I wouldnīt worry too much just yet about the salary on offer at Easy etc if / when you get a job on the 737 etc in the UK you will find out exactly for yourself. When that time comes, you wonīt be able to live like Wayne Rooney, but you will have more than enough to get by
Get looking into CTC and other ab-initio programmes and seek advice from as many people as possible, most will be more than willing to help
Good luck