Liam,
The speed at which the application process is completed is pretty much determined by you. The quickest you could clear all three stages is probably less than 10 weeks from the date of your S1 assessment to your medical clearence.
In reality however most take a little longer, choosing to research the role between Stage 2 (FEAST Tests) and Stage 3 (Competency Interview) including making tower visits and generally preparing themselves for what is a tough process.
If you were successful now, I think the next start date you are likely to get would be November 2010 for an Area course, or April 2011 for Aerodrome. As you are just starting the process, I would expect that is you completed the assesment phase in an average time then you would be looking at a mid 2011 start date.
Travel expenses are on your head until Stage 3, and then only expenses greater than £50 can be claimed back.
Hope that helps.