The simple answer to your '"how long?" question is almost certainly "Forever". Once your details are on the UKBA database, as a suspected smuggler, it's unlikely that they'll be removed.
Madmaggot refers to your actions as 'illegal' but, as long as they are genuinely for your own use, you can bring back an UNLIMITED quantity of cigarettes from any EU country. The 3200 'limit' is simply a guideline figure, above which you're more likely to be challenged about your imports. If you believe that your ciggies were seized unlawfully, you should have followed the appeals procedure:
http://customs.hmrc.g...propertyType=document
(The fact that you didn't might look bad when UKBA staff check their database).
However you might like to think yourself lucky that you weren't arriving via a ferry port. The usual procedure there, in the case of excessive tobacco imports, is to seize both the car and the vehicle.
Chris