hi all,
thanks to Matt - it helpd me s-off

cheers
i rooted my phone before using Unrevoke and so had clockwork 2.5 installed already
once s-off i used android flasher from SUs post elsewhere to flash the cm7v2 hboot
*BEWARE* once the hboot flash had run my phone appeared to be hung in htc boot screen! scary for me
BUT, i pulled battery and then booted into hboot-> recovery as normal ok - so was then able to wipe wipe wipe and re flash cm7