Ok, think ive sussed it… I have a shimano TL-HG15 which works for normal cassettes. I think righty was right and i need a different tool TLFW30 as my hg15 doesnt fit into the middle of this freewheel cassette. Looks right but must be just off. I have removed the axle from this.
righty, how much do you want for that tool? – bearing in mind that i will only use it probably only once.
Once i get this off i pressume i cant use a standard type of cassette conversion kit – what kind of rear singlespeed sprocket will i need? something like this : http://www.velosolo.co.uk/dicfree.html
And by the look of it another tool to then tighten this on – this project is turning into a major pain in the arse.
Big thanks for the advice everyone. cheers.