Smyle was appointed to run the project at the Silverstone Wing this week, with Citroen dealers attending a dedicated event on 11 December, before the venue was re-rigged for Peugeot dealers on 13 December.
Around 800 Citroen dealers and 1,000 Peugeot dealers were expected at the event, although final numbers are currently being evaluated.
Citroen's national events manager Neville Staines told C&IT is was a "stunning event". "It was absolutely fantastic," he added.
The move follows a closer relationship between the two brands after Citroen moved from its Slough base to Peugeot's Pinley House headquarters in Coventry this year.
Until this year, PSA Peugeot Citroen was the only automotive group in the UK to have separate head offices for its brands.