Thanks, Spanners, I was looking all over for that sort of info, but obviously in the wrong places. It was my typo but Palominos and Thoroughbreds are sweet mystery to me.
Interestingly though it does require the 133 Mhz speed setting after all, the only change I made was to force a >12.5 clock ratio rather than leave it on the automatic setting. This gives the correct 1.74 GHz processor frequency and 2100+ identifier and apparently operates over a 266 MHz FSB (I think this is something to do with the DDR RAM using the up and down sides of the clock pulse).
It's all runnung just dandy-o now and I await my new graphics card with baited breath....