Thanks for the replies.
@ pitboot, I checked when I got my poles, I was given them for Christmas in 1998, so they're 20 years old! (I found a mention I made on a 1999 trip report!) The grips look a very tight fit on the poles, they don't look as if they can be removed. There's a plastic stud on the top of the grip but I don't want to start poking around there.
However, I found a link to Leki spare parts. They didn't show mine, but it says under one type, "This grip is just one example of the grips available. Please contact us at
[email protected] with a picture of your poles if you would like a quote for replacements for other types." So I shall do just that.
@ kinkyboots, your suggestion of cornstarch (aka corn flour, I have learnt, which the OH says we have in the cupboard) would clean the grips, but is it likely to remove the stickiness after my attempt at cleaning them? I shall try talc first (another thing the OH has!) but I rather fear it is due to degradation of the material as pitboot suggests.