I found this benchmark (old times benchmark) PCW Benchmarks (http://www.geocities.ws/peterochocki/computers/pcwbm.html)
and tried it on winape (cpc464 emulated).
CPC Basic 1.0 seems to be 3,75 times faster than Spectrum.
CPC 464 (Basic 1.0) / Timing in Seconds (TIME/300)
BM1 1,127
BM2 3,43
BM3 9,35
BM4 9,8
BM5 10,39
BM6 19,33
BM7 30,81
BM8 34,48
average: 14,83 (3,75 Spectrum-times)