I had a bit of time on my hands over Xmas so I decided to tackle the dismal headlights. I replaced the earth cables and connectors and wired the new ones straight to the battery -ve, one from each headlight. I used 17 amp cable. Then I fitted a relay, using the old headlight dip beam (off side) wire for the relay coil and fitting new 27 amp cable back to the battery +ve and to both headlights on the switching contacts. My God, the lights actually work now, and although they are still only 'quite good' they are a long, long, long way better than they were. Only one minor niggle to sort out, the lamp failure warning, but I can live with that now I can see where I am going at night. I can now see signs, the road edge, white lines, cats eyes and even with oncoming traffic.
The old connectors on the earth terminals were 'blued' from heat or poor connection causing resistance and therefore heat I presume. All fixed now.
This helped me lots, I hope it helps someone else.
Incidentally I am using the Osram Nightbreaker bulbs and they are very bright (now).