Might be a poor quality extension perhaps
. Anyway, these guys do 20m plus cables:
evcables.com
Looks like they deliver to Europe too.


Type 2 to Type 2 EV Charging Cable
Type 2 to Type 2 EV Charging Cable available in 2m to 50m. Next Day Delivery. 2 Year Warranty. 30 Day Returns. Engineered for Safety and Reliability.

Looks like they deliver to Europe too.