Actually, if you're serious about this, then a class 1 medical has to be your first hurdle. Get in touch with Gatwick and book yourself in - no point in going any further until you've got that done.
I can thoroughly recommend Clive Hughes' book "Guide to getting a professional pilots license", and read it cover to cover a few times just to see what this all entails.
http://www.ppl-atpl.demon.co.uk
I did it all while working, under the CAA system so yours would be slightly different.
I did the PPL on the weekends (took 11 months due to the lovely UK Wx)
Went of to the States to build some hours, do a multi rating and some night flying.
Did the ATPL writtens by correspondance course (Thanks Bristol!!
)
Then did a BCPL followed by an approved CPL/IR upgrade a bit later on.
It took me three years altogether, throughout which I was constantly building hours and studying. Considering I have two jobs as well it was knackering, and I passed most stuff first time too, so it could've taken longer.
I've only just done an MCC course though, so perhaps we could say a little longer than three years.
I would say the work has to go once you get into the commercial license stuff - I took my paid leave for the BCPL (three weeks - JAA CPL will be more like 5 weeks) and unpaid leave for the CPL/IR (13 weeks), for these courses you really do need to be on top of your game, doing it part time isn't going to work unless your very experienced or very very good.
I understand that nowadays the "distance learning" part of the training is likely to take a full year as well, don't forget there's a mandatory class room element for this.
I have not as yet done an FI course and am concentrating on building multi hours, so you may want to factor that in as well if you intend instructing at all.
All the best, it ain't easy but you will enjoy it.