reflectors and brake lights
bmwgs, you are mistaken about the reflector, the law states that NO LAMP OR REFLECTOR need be fitted if there are no font and rear position lights.
As for the brake light, there is no reason why you can't fit one at the time of test as the ALL OR NOTHING only counts if you have front and rear position lamps.
If you do fit a brake light then it must meet the current regulations, so I presume that this means actuated by both the front and rear brakes on modern bikes.
A useful link is http://www.motuk.co.uk/manual/mc_contents.htmthis is the manual that MOT testers are meant to refer to if they are unsure, but many testers appear to guess instead.
The lighting regulations are at http://www.legislation.gov.uk/uksi/1989/1796/made
this is where the CPS will look if confused Plod tickets you, the relevant bit is Section 4(3)(a).