Andy Hall wrote:

There are some plugs that I found on the Screwfix site 89036 which go
into a drilled hole and then a cable tie can be attached. I bought
some and they work well.

Yep, I'll second the vote for these plugs, especially if you are running
multiple cables; BUT beware the effect of UV light on the ties. Unless
a special grade is used they can fail in 3 years. (seen it, replaced
them, got tee shirt etc)