Your conviction became spent after 5 years (or 2.5 years if you were under 18 at the time). You never have to declare it for all 'normal' job applications (even if the application form doesn't tell you that you can ignore spent convictions).
The only time that you'd be obliged to declare the conviction would be when applying for posts where the provisions of the Rehabilitation of Offenders Act doesn't apply. They include jobs working with, or alongside children or vulnerable adults or employment in association with the 'administration of justice' (e.g. with the police or alongside them in certain civilian roles). In practice such a conviction would be extremely unlikely to adversely affect any job application for these types of employment.
With the exception of the types of employment referred to above, the law allows you to 'answer accordingly' (i.e. lie) when asked a question relating to convictions or to a related matter (e.g. If you were asked "Have you ever had your insurance premiums increased due a driving conviction", you're allowed to say "No", even if it's not true).
http://www.lawontheweb.co.uk/rehabact.htm
Chris