new regs been brought in this jan 2012, are non standard aftermarket led lights fitted into external lights on vehical will bring an instant fail to mot, but hasnt fully come into force as yet... so kind of a grey area, mot & police discresion... so some mot stations will fail it others pass, some police jump on you £30 fine, others ignore you...
...but to be honest a police traffic cop friend says they would rather people have fully functioning lights led or filliment as long as they are in pairs, dont dazzle other road users, work correctly (led indicators flashing like hell) & correct colour i.e NOT BLUE GREEN PURPLE RED etc than people not caring with a unit not working i.e (blown bulbs)
But if not E marked & state off road use only you run the risk at a fine sometime or mot fail...