I think I should withdraw this suggestion, as although one of the reviews states that it meets the JASO and API specs I can't find any definitive information from Halfords to confirm this. I have never used it myself.
I have used the Castrol Power 1 Racing oil in the past and the following is the information on this from Castrol's web site:
Castrol Power 1 Racing 4T 5W-40
Co-Engineered with BMW Motorrad*
Description
Castrol Power 1 Racing 4T 5W-40 is fully synthetic 4-stroke engine oil for modern high performance sports bikes that increases engine
acceleration and power right up to max rpm.
Its Race Derived Technology based on Castrol’s racing history and testing experience ensures maximum engine performance without
sacrificing engine durability thus giving a significant benefit over other types of engine oils.
Castrol Power 1 Racing 4T 5W-40’s formula employs the very latest Trizone Technology™ for 4-stroke motorcycles, so as to give optimum
protection of the engine, clutch and gears even under the most arduous riding conditions including sustained operation at high rpm.
Application
Castrol Power 1 Racing 4T 5W-40 is suitable for all modern high performance motorcycle engines where API and or JASO specifications are
recommended. It is specially approved by BMW for K1600, K1300, K1200 models, S1000 RR, G450X. It can be used in several motorcycle
gearboxes, where delivers excellent clutch performance.
Advantages
- Ultimate performance in extreme riding – oil flows fast and stays strong, reducing internal engine friction
- Tested and proven to deliver exceptional acceleration at the touch of the throttle
- Fully synthetic 4-stroke motorcycle engine oil featuring Trizone Technology™
- Race Derived Technology for max engine acceleration.
- Extreme high temperature air-cooled and water-cooled engine performance.
- Excellent high speed oil consumption control and volatility.
- Excellent shear stability to prevent viscosity break down.
- Complies with requirements of catalyst equipped engines