Yes, you have to declare the convictions.
Applicants for UK citizenship have to show that they're 'of good character' which means that they have no criminal convictions. The Home Office would almost certainly refuse an application from anyone with an unspent conviction. (If you were only banned from driving, and not fined, the convictions become spent as soon as the ban ends. If you were also fined, the conviction becomes spent 5 years after the date of conviction). However, the Home Office is not obliged to disregard spent convictions. It's still unlikely that they'd grant you UK citizenship when the conviction becomes spent unless your application was made a considerable time (e.g. 10 years) after the conviction became spent. (Even then, you might still be refused).
Chris