Ok I am hope I am not to late on this for you Mox1968. I myself am a boiler tech. so I was surprised when I didn't recognize the name of this boiler when you posted this, but with a little help from the internet I got a better grasp on it. First off, I see this is a UK boiler and that is why I have never heard of it. Anyways, like I said I researched this and came up with a manual for the unit I believe. You will have to look it over and see if it is the same unit first. Also if it isn't let me know and I will search a little more. From what I have found out by the manual you can't replace the bearing to this fan or lubricate them. What you can do and which I suggest is to just change out the fan. There is a section that gives the fan part number on page 54, with that number you should be able to order and new fan. Now for changing out the fan you can go to page 32 and it gives you a step by step procedure on how to do this. You can print this manual off at the following link: RavenHeat CSI 85T
I hope this finds you in time and it is the correct unit, because it seems to be an easy fix. Please let us know how this turns out for you.