sprinty, madmax, Burgundymog, HARPy chappy, Stringers Best Mate, cereal surfer, Gamabalunga et al,
Many thanks to you all for the feedback and advice. Really helpful. It was BHM themselves who raised the concern but good to know HARPy chappy passed at Goodwood.
For peace of mind I'll try and get a test done before going down - a bit of You Tube research indicates a stationary test at 3/4 max rpm (not convinced that this has any direct relation ship to pass-by noise under load but hey-ho). Madmax, thanks for the offer of help with a test - I'll send you a message to try to set something up.
Ian