Okay folks - I did the deed at the weekend,it worked, and here's a summary. Note! It worked for me: YMMV.
- Cleaned off what appeared to be a semi-solid impact adhesive from the pseudo-rubber "push" button- don't lose the centre spring! I used extreme care and the edge of a vegetable knife as a scraper;
- Mixed a portion of Araldite Rapid,about the size of a filter-cigarette tip;
- Moved the flash head so that it's vertical;
- Try a dry run: place the rubber button into it's correct position and make sure no bits stick up. When you're happy,
- Applied adhesive carefully to outer edges of the button and also carefully to the corresponding metal area on the SB-600 and join the rubber to the metal;
When you're doing this initial lining-up, try and get the lettering that says "push" to be the correct orientation!
Wrap your button and flash gun with Sellotape (clear tape) and leave it for an hour: longer if you can. Depending on the ambient temperature, you may want to clean off any excess.
Hope this helps!
(NB.. Some adhesives seem to based on flammable compounds, and I was reluctant to use these on a device that can generate kilovolts, and sparks)