If it has been 5 years since your conviction, you don't even have to declare it ever happened and it doesn't show up on the Disclosure certificate. Hence the term 'spent conviction'. If this if the case for you now or by the time you start applying for jobs, you have nothing to worry about.
A good friend of mine was in you predicament and was naturally concerned. After graduating oxford in 2003 he got his first jet job on 737s a few months later. He's now on the airbus and loving it. No one ever asked him, he didn't volunteer it and has no obligation to either.
If flying is what you want and you're determined, I wouldn't let this slow you down anymore than it already has. It happened, you paid for it, you know it'll never happen again, so why re-live it. I wouldn't listen to the judgemental individuals on here either, they have no idea what they're talking about. Our more positive friends above seem to be a little more objective and that's nice to see.
Best of luck and enjoy the flying,
atcs