[5] Driving for Fortec Motorsport, Buller took twelfth in the championship standings, taking the fastest lap at the final race at Monza.

[6] Buller also made a guest appearance in the Formula BMW Americas series, driving for Autotecnica at the Canadian Grand Prix-supporting rounds of the championship.

[7] A first win proved elusive, although he did take a pole position at Silverstone,[8] and also finished third at the Nürburgring,[9] en route to tenth in the championship.

Buller made a guest appearance for EuroInternational at the final round of the Formula BMW Pacific championship in Macau.

[13] In 2013 Buller started the FIA European Formula Three Championship with Threebond by T-Sport driving a Nissan powered Dallara F312.

However, despite tying with teammate António Félix da Costa for best victory of the season, Buller was not retained by the team for 2013.

In 2013, Formula Renault 3.5 team Zeta Corse confirmed Buller to be their sixth driver in only four race weekends after Emmanuel Piget, Mihai Marinescu, Mathéo Tuscher, Carlos Sainz Jr. and Nick Yelloly.