Here are some recommended options:
1. Castrol Syntrans 75W/80: This fully synthetic gear oil meets or exceeds the SAE 75W/80 API GL-4 specification and is suitable for use in your Rover 216 with the 1.4L K-Series engine and R65 gearbox.
2. Comma MVTF SAE 75W/80: Another reliable choice is Comma's Multi-Vehicle Transmission Fluid (MVTF) in SAE 75W/80 grade. It meets the API GL-4 standard and is designed for manual gearboxes.
3. Valvoline Syntrax Universal SAE 75W/80: This high-performance synthetic gear oil from Valvoline meets the SAE 75W/80 API GL-4 specification. It is formulated to provide excellent protection and smooth gear shifting.
Always consult your vehicle's owner's manual for the recommended transmission fluid type and capacity.