The 14-year-old rider finished third overall at the Knockhill Circuit, in Scotland.
It proved a successful weekend for Buchanan, of Invercargill, who opened with fourth in race one before securing third in race two.
"I have no words to describe how I felt crossing the line in P3," he said.
“My family has made a lot of sacrifices to help me achieve my dreams over here and it feels unreal to reward them with this.
"It’s only the start and I strive for more in two weeks in the next round at Brands Hatch."
Testament to the tightly contested battle on track, Buchanan was pipped on the finish line for second by just 0.2sec, England’s Johnny Garness snatching the honours.
“I had to be very aggressive in that race since I knew I would lose time on the straight against the smaller, lighter riders," Buchanan said.
“I knew a podium was on the cards and went for a lunge on the second-last corner to reduce the distance to second. I sent it into the final corner, pulling off the move but unfortunately he got me back down the home straight.
“I loved racing in Scotland. The track was fast and had some really technical elements and it was really special to be here where my ancestors came from before my great-great-grandfather sailed to New
Zealand in 1919."
The results have boosted Buchanan to sixth overall in the championship standings after a challenging first round at Oulton Park.
After crashing out of contention in the opening race a fortnight ago, he was forced to start from 31st on the grid and scorched through the field to earn an impressive fifth overall.
Buchanan, who was recently named junior sportsperson of the year at the ILT Southland Sports Awards, is competing in the British Talent Cup in the United Kingdom with the Microlise Cresswell Racing team while being based in the northern hemisphere, where he is the first New Zealander selected to contest the prestigious Red Bull MotoGP Rookies Cup.
Featuring 26 riders from 16 nationalities, the Rookies Cup races at international circuits throughout Europe alongside the MotoGP.
Buchanan will remain in the UK for the next two rounds of the British championship before heading to Austria for two rounds of Rookies Cup in August.
His racing assignments then take him between the UK and Spain.
He will return to New Zealand at the end of October to link up with the Yamaha Racing Development Team for the New Zealand Superbike Championships, with the aim of defending the 300 SuperSport title he won earlier this year.
