was the battery you hooked them up to any bigger than the cars battery by any chance?
all hid kits like a really really good current and voltage supply, along with super clean earth connections, such is the nature and sensitivity if digital ballasts i suspect, which have a hard job to do it has to be said.
some perseverence should see it working fine, but deifintely check you have a really good battery and earthing.
just a quick note on the current stance of mot regarding retrofitted HID kits, in particular, aftermarket kits, not manufacturers oe kit from an option list or higher spec car.
it states that a vehicle fitted with a none original hid kit, must have fully functioning self levelling adjustment, and headlamp wash system.
this was due to be implemented in the first quarter of this year, and i'm not sure if it made it in or not, but in essence, just passing the beam pattern test is no longer enough, as they are actively trying to legislate this sort of modification off the roads, due to the complaints and issues surrounding poorly fitted kits.
this will land me in a stir just as much as you guys, so don't shoot the messenger, i have been HID'ing for years!
and swear by them when done properly too, stuff the law, for mot i simply put the halogens back in now, which is hardly difficult seeing as most kits take their relay trigger from the original lamp socket anyway, 109 minutes on a tricky car, done.
so keep at it, the rewards are well worth it IMO
incidentally, i would dearly love to HID my Sprint, but as the reflector bowls are tired and have lost some surface coating, its a waste of time, the headlamp unit itself has to be in good nick first, otherwise there will undoubtedly be some light output gain, but uncontrollable!
good luck mate