For an MOT,
hazard lights must have a visible warning light (or lights)
indicators can have either visible or audible, that is to say, if the visible isn't working then it won't fail as long as there is a working audible warning.
(This doesn't follow "if it is fitted it must work" rule. Elsewhere it does say that all warning lights must work?)
MY MOT tester, who i've known for many years, is very bright, very experienced and has an encyclopaedic knowledge of the rules and regs. I've HAD failures for non working indicator warning lights and the justification is that the "either or" reg is exactly that! If the car came from factory (or kit) with NO warning light, an audible warning is OK. But if it HAS got a warning light, (or two) they MUST work, irrespective of the audible part.
NEW regs, as of this May gone say that ALL warning lights on the dash must work and ANY warning light on that shouldn't be (ie engine management, pad wear, choke light staying on and other inconsequential rubbish) is now grounds for failure! Unlike some of the other new rules, this one is NOT age related, so when you take your Dolly in for test (if you do) make sure the handbrake light works correctly (and the PDWA if it's a dual circuit car) and the choke light goes out when it's fully home!