Wendy has been called Britain's last girls adventure comic and the reason that most people haven't heard of it is because while the Wendy comic strip is written and produced in the UK, it isn't published here. Wendy is a popular and much merchandised German comic that is a co-production between Egmont and DC Thomson and tells of the adventures of a horse riding teenager, Wendy Thorsteeg, and her family and friends at her family's stables. There are more details of the comic over on Bear Alley.
If Germany isn't quite far enough away for you, in the mid 1990s New Zealand television produced and broadcast a live action television series based on the comic strip which they called Riding High and in which they rechristened the characters with less Germanic names, Wendy Thorsteeg becoming Wendy Thorburn. You are unlikely to have heard of it as Riding High has not apparently been screened in the UK, although it has been screened in the Republic of Ireland.
However when Riding High was bought and dubbed for broadcast in Germany, the 65 half hour episodes were rechristened Wendy, the characters given their original names back and it is those German episodes that are prevalent on You Tube.
The young Karl Urban (in blue in the back row above) was a regular in the series as James Westwood/Jerry Kiesemann, the boyfriend of Wendy played by Marama Jackson, and so was riding horses long before he ever rode a Lawmaster.