With Scottish passenger Jimmy Connell, the pair suffered a crash during qualifying before the LCR Suzuki developed brake problems during the first race.
The final two races always attract double points and after completing their two races in seventh and sixth place, the duo ended their season in seventh with 151 points.
Horspole said: “That’s year 31 done and I find myself seventh in the British F1 championship which is my best in this class; bring on next year!
“Many thanks to James Connell, my star performer, and to my parents who at even my age I could not do it without.
“Also I have to thank my sponsors and supporters who have stood by me through thick and thin: Sleaford Quality Foods, Baker Plant Hire, Oxford Products for our HJC helmets, Avon Tyres and everyone else who has helped us over the years.”
Free practice went well except for the brake issue, but during qualifying the problem caused the outfit to crash at Paddock Hill and turn upside down which brought out the red flag.
Luckily neither was hurt, except for a few bruises, and prior to the crash they had done enough to be 15th overall – eighth in their class – to start Saturday’s race from the eighth row.
The outfit didn’t suffer any damage in the crash, but the brake issue was still causing problems and they rode a steady race to make sure of a finish.
They were 10th on the opening lap, but dropped back to complete the 10 laps safely in 12th place overall, and seventh in class, to pick up 18 championship points.
“We were unable to solve the brake issues in time for the first race so we just cruised round to get some points,” Horspole added.
Having discovered the problem, the pair set out to be more competitive in final race, and started from the sixth row.
Horspole and Connell made progress up to 11th at the chequered flag, but were pleased with sixth place in the F1 class for a respectable end to the season.