Drink driving is a serious thing and not a menial issue.
You are right you are very very wrong and at 25 thank god it is your first and hopefully last conviction.
You will struggle to find work with companies who need CRB checks as these show criminal convictions. You will need to be close to home unless public transport is readily available where you live.
An awful lot of job application forms ask for details of criminal records and you are going to struggle.
However, I would check your contract about instant dismissal for cpnviction - I used to work in bank and never heard of this before unless for stealing, fraud, etc.