It's a little hit and miss really - it's very possible that he's driving the banger because since the ban, his parents have cut him off financially, and he can't afford anything else - no bloke is going to impress a woman with the line "well the car is a piece of crap, but I can't afford anything else".
In regards to the drink driving, this has been well answered - working as an insurance fraud investigator, I can honestly say I've never seen a drink drive conviction that DIDN'T carry a ban.
It's very probable that this guy is lying, but have you thought that it may not be because he's being malicious, but just because he's embarrased - everyone makes mistakes.
Whilst I know I'm opening myself up to a barrage of abuse from the women, this sounds a little more like jealousy than looking out for your mate. You've obviously been digging for information on this guy to find out about his drink drive conviction.
In regards to the teaching profession, yes if he went to prison for drink driving, it will show on his record. However, under the rehabilitation of offenders acts, and general common sense in some cases, this won't affect him getting any jobs.
Let's face it, paedo's can work with kids, so ****** behind the wheel won't make a difference.