Well I have decided to conclude my HID experiment and so this evening I uninstalled the HID's and went back to normal H4 bulbs.
While I wasn't impressed with the HID's, I was going to leave them in, but recently I have had problems with the kit. One of the ballasts started playing up, not always firing up, so I got a new ballast which was fine for a couple of days..... so I went back to the intermittent one.
Then today, both failed to ignite. I did the simple thing, checked the fuse which was OK, but decided then that enough was enough. If the HID's had been good, I would have tried to resolve the issue but since I don't think much of them I decided it wasn't worth the effort.
I'm glad I have tried HID's. I would not have been satisfied until I did. They were definitely mega-bright to look at - a few people commented how bright they were when I followed them. I just don't think the light unit on my ST works very well with them. I would try them again on another bike, and I would also try to track down a decent kit rather than a crappy one.
I've ordered some Osram Night Racer bulbs, I've used these before and they were pretty good and lasted well so I will try these again. It will be interesting to see how they compare to the HID's.