3rd brake light - MOT failure?

[thefifeflier]

On my car's annual service last week, I was told that 2 or 3 of the LEDs in my high-level 3rd brake light were blown, and that the unit would have to be replaced at a cost of £150 as it was an MOT failure.

Not entirely convinced, I said I'll wait until the MOT was due, to do something about it; when I got home I looked into a bit further on the Interweb. Firstly, I found I can get a replacement fitting from the States for $32, and secondly I found this website which may prove quite handy for future reference:

http://www.ukmot.com/Your-MOT-Questions/Brake-Lights

So according to this website, 50% (at least I'm assuming it's 50%, as the % sign was omitted) of the lights in the 3rd brake light must be working for it to pass. However, I'm sure I read somewhere else that it only needs one bulb to be working in order to pass!

Any thoughts, folks?