Not really a grey area.....
"Existing halogen headlamp units on vehicles first used on or after 1 April 1986 must not be converted to be used with high intensity discharge (HID) or light emitting diode (LED) bulbs. If such a conversion has been done, you must fail the headlamp for light source and lamp not compatible."
IIRC this was brought in as a "fail" sometime last year although I have LED bulbs in my headlamps and the beams are OK so it passed the MOT last Sept. It's due again in a couple of weeks. I still have the halogens to refit but intend to leave the LEDs in and chance it.
This has come in since I fitted mine and since my tester commented, it was a grey area at the time.
Like I say, keep a pair of spare candles, sorry halogens, somewhere on the truck and change if need be, or if concerned, change before the MOT. With properly aimed good quality LEDs with a perfect beam pattern, I don’t see the issue. A common sense approach would say that if the beam pattern was poor it should fail. In other words if they were going to cause problems on the road. Common sense however is in short supply these days.
Though you may find some that don’t say ‘For off road use only’ they won’t say ‘legal for use on road’ either.
The issue with LEDs and more so HIDs in lenses designed for halogens is the filament position is set for halogens. Unless the light source exactly mimics the filament of a halogen lamp, it won’t be in exactly the same spot.
The thing is, I can’t imagine the likes of Phillips designing and tooling up for something dodgy. I also imagine them lobbying the DoT to get sensible guidelines in place. Whether or not this happens remains to be seen. As it is, the change in ruling is a blunt instrument.
So, going back to the original question, the answer is to look for after market HID or LED headlamp units. I know they are made for the 80 but as far as the hundee goes, I can offer no further assistance. If you intend to be squeaky clean then I wish you luck finding them and look forward to seeing the result. One place to look might be the makers of the 80 ones to see if they do ones for the hundee.
@clivehorridge and
@Chas have/had these fitted as well as one or two others.