Hi,
You will find a wealth of information on this forum, you will need to keep your eyes peeled for a TOC (train operating company) to advertise for trainee drivers also when they put the advert up and it's quite often removed in a short time.
Also you are usually required to live within 45mins/1hr of a depot so that will have a bearing on what TOC's you can apply for.
It can be a long old wait too! Even if you apply, your application will need to demonstrate potential to be able to do the job your application may not make the initial sift
You will the be invited for a selection of tests (search forum) and 2 interviews
Then you may only sit in a talent pool as for every job around 3-400 apply!
I applied in October 2014 for A TOC and have been Lucky enough to be starting as a trainee driver in March 2015. 6 months is very very quick, For some it's not so quick waiting for 2-3 years is not uncommon and having to re-apply because your selection test passes have become expired.
But I wish you the best of luck, I found all the info I needed on this very forum.