I doubt you'll get another crack at it, I may of course be wrong. HR are the only people who can help you with that so best to contact them and they may let you reapply.
As a driver you need to make sure you are prepared and aware of your actions, if you make a mistake there may be very serious consequences. You need to get things done correctly first time, I don't imagine asking to re-do an application form will win you much favour.
I was told by HR once (not at my current TOC) that mistakes on an application form meant that applicant was instantly binned. The view was that if someone can't take time and produce a fault free application when in the comfort of their own home with no pressure then how poor would they be if they had the job and didn't have that luxury. To a certain extent I agree but there are great train driver's who aren't amazing when it comes to spelling (crosswords left in the bothy shows this
). There's no excuse on an application though as spell check or even a dictionary solves that problem. It's sometimes worth letting someone else read through your application too if you have someone that can do that for you. In my opinion it's the most important part of the whole application process as if you don't get it right you can't progress. Manager's will also have it on hand if you make it to DMI.
Hope you manage to get it sorted and if not then at least you can put what you've learned into the next application.