Might be one of those where i go "oh right" but i've just bought some new grips and they came with a tiny little cable tie with each of the grips.

What they for then?

Are they slip ons? Maybe to wrap around one end and tighten up like mad to make sure they don't slip off…?

Yep they are slip ons but have caps on the end with screws to tighten like a plasterboard wall plug if that makes sense? so thought that would be enough??