I have just fitted a WOSP starter motor to my B20, and it is entirely satisfactory, straightforward if inaccessible fitting. The car starts instantly with no churning over.
I know Luke Wos personally and Wosp's products are used all over motor sport and small volume makers, GT and Le Mans cars.I would vouch for them and have developed products together with them for both Lambda (starter motors) and Aurelia (alternator with eccentric adjustment).
I would not hesitate to recommend