Developed quite a severe notch, which got worse suprisingly quickly..
Performed the Gonzo tweak, and it cleared it up completely and I got through my MOT this morning with flying colours..
I was a bit worried that being a second hand bike I would perform the tweak and then find that the previous owner had already beaten me to it, but no problems there.
Also a big thank you to Jim who kindly helped me with his organised compilation of notes on this topic.
One last thing worth mentioning, the steering is so much lighter now, but without any play in the steering tubes. Much easier to steer the bike now.
If any of you think your steering is a bit heavy, might be worth looking at the tightness of your steering head nuts and having a play with slightly lighter torque settings to see if you can improve matters.