Riki's final season of karting came in 2006, when he had another 2nd – this time coming in the European Championship – beaten only by legendary Italian Marco Ardigò.

Driving for Fortec Motorsports team, Riki finished 5th in the championship, which was dominated by French interloper Franck Mailleux.

Riki had a solid season, with 7 podiums including a maiden victory coming at the final round at Thruxton leaving him sixth in the championship.

[3] A sophomore season of FRUK occurred in 2008, and again Riki scored consistently, with nine podiums and two wins for a fifth place overall championship standing.

[5] Riki took his first win in the series at Snetterton, holding off championship leader Daniel Ricciardo, Walter Grubmüller and Renger van der Zande.

Christodoulou returned to Formula Renault UK in 2010 for the last half of the season with CRS Racing for one round, then Fortec Motorsport for the latter and finished 11th in points with one win and four podiums.