I'm just about through my professional training (final few weeks of Multi IR) and am also sponsored by an airline so here's my experience:
PPL + Night + IMC + 100hrs P1 rating took me about 1year although I spread it over a 4 year period while I was at university. Once through all the basic stuff and proudly waving your dysentry beige coloured PPL you need to get your ATPL exams. FOr guidance I did the JAR course at PPSC which took me from July 2000 till April 01 to get all 14 of the bastard exams that JAR insist you sit. That is the killer as you don't get to play with aircraft until you're through all the exams. If you have the time / money then do take the full time course at a REPUTABLE school.
SO now you have your ATPL exams passed you need to get your CPL and IR done. bank on 4-6 weeks for the CPL (25HRS with 7 in a complex single minimum). The IR takes longer so bet on 6 - 8 weeks but weather isn't as critical here (IR=20Hrs SIM and 35 in a twin). Once that's all passed and you are about 25-30K worse off you need an MCC course in order to get a multi-crew job. So really you're looking at about 200-250 Hrs on completion of training.
My company flies it's crews about 350hrs a year but we do short sectors at unsociable times so it's the FLight duty period that gets us on that. SO all told I'm looking at about 4 years before I get my hands on the ATPL Holy Grail.
Hope that helps, if you have any questions just e-mail me at
[email protected]