I read somewhere of a 6 months statute of limitation for being taken to court.
I love it when posters ask us to comment on unattributed bollox they allegedly read somewhere on the internet.
There are 2 possibilities - either you did not read that, or if you did whoever posted it is a moron.
As you claim to have received an FPN (as opposed to a COFP), for an endorseable offence, and received advice from the DVLA about it, the second possibility is perhaps not the clear favourite that it might otherwise have seemed.
For most summary offences, including speeding, the police have 6 months from the date of offence to instigate proceedings by issuing a Written Charge and either a Single Justice Procedure Notice, or Postal Requisition.
There has never (or at least not within living memory) been a requirement to get the accused into court within 6 months. It has always been to instigate proceedings.