Don't whatever you do fail to declare the drink driving offence, it could invalidate your insurance completely.

Your speeding offence is valid for 3 years, but stays on your licence for 4 years.  The drink driving offence will stay on your licence for 10/11 years.  I think that if you commit another drink driving offence within 5 years you'll receive an automatic ban of three years.  Just check on the DVLA site though, it's a few years since I worked in the court service.