Ok, so it's all done and I won
I did a bit of dremelling behind the race and it worked a treat. A gentle pop with my new and more suitable stick, er, I mean drift, and it came out no trouble. my thinking with the dremelling is that I didn't have a surface that the drift didn't just slip off before, so how tight or loose it was was of secondary importance. I went maybe a mm deep, I'm sure that won't make much difference to structural strength. There's 2 much bigger ones at the bottom anyway from a previous owner. I ground a notch and got it shifted a mm or so. Then did the same again at about 120 degrees to the first, and then a third... then just tapped it out a bit at a time.
The new race has a much bigger lip, so will come off no sweat. I don't think the one's I've taken out are original since there are pre-existing notches at the bottom, so maybe they are just particularly skinny ones. I've tried taking pictures for others attempting it, but my camera isn't up to it.
I did dremel into the race itself slightly, but I used a flat top grinding piece, putting in a new unworn one to do the mm vertically just below the race so it was flat. Because the ground surface of the race is still perpendicular to the drift it still knocked it out. The races are a lot harder than the steel of the frame as well of course; impressively hard in fact. I don't know what alloy they are made of but on experimenting I could barely make a scratch with a hacksaw.
Putting them in wasn't much trouble, having used the freezer trick (ta
) although I put together a puller using a M10 thread thingummy and massive washers which I got off the forum somewhere and is in the Haynes.
The top of the top race is flush with the top of the frame housing when right in, so that will go in no problem with an 'ammer, just tap it flat. The bottom one would go in using the hammer and the old one on top as a guide so it can push further than flush with the edge of the frame tube if that makes sense. It's deeper in than the top.
So I thought I'd brain dump for if anyone else is doing it. If you are and the above might be helpful but I haven't been clear or owt then let me know and I'll try and let you know what I did, assuming I can remember;)
Here's a picture, which I did before noticing that 69oldskool has described the same idea of pushing the drift away from the tube to keep it tight under the race
The drift I've used is a 30cm long 10cm diameter rod of silver steel which is nice and hard with a suitable edge for the dremelled ditches, and you can get from a decent trade shop for 3 or 4 quid.
Cheers for all the suggestions on here. Even the ones I haven't done are good tips and I've learned something for the mental toolbox for the next problem, and for the next people doing this:)