Changing cassette on bike rear wheel

goodValue

Are you sure it is a cassette not a screw-on freewheel? 

Thanks for looking at the details of my post, I think you are the only one to understand the issue.
I didn't know that the old style cassettes (that don't need a chain whip) were still being used.
A splined removal tool fitted into the cassette, and so I didn't even think it could be the old style (I thought the removal tool for the old style cassette always had notches rather than splines).

When I get back, I'll have to check if there is a replacement cassette first, as I think there may be a problem with availability.