Well I do worry about the chain as it will be cutting into the tree.

You can get soft adjutable straps for wrapping round trunks that perhaps you could attach your chain to?

Can't help with the moths and don't grow apples, but I did see a suggestion of wrapping corrugated cardboard round the trunk so the moths will spin theif cocoons in the grooves, and you then take it off and destroy it when they have done.

Good points Stera

The trap is only an indicator of the presence of Codlin moth. When you see them trapped in it , then it is the time to spray the tree with insecticide.
The Winter spray is a Horticultural soft soap which is applied on a dry windless day in Winter (January ish). It kills off any overwintering bugs in the bark and their eggs. It does reduce the incidence of attack, but once you get them, then they are almost impossible to eradicate.
Apples with moth damage are still edible, at least the bits untouched are.

Thanks very much. I think it was O.B. Who gave me this info once before.
And I'll look to the chain tomorrow morning
I have corregated cardboard in the loft and will see to that tomorrow too.

OB would this be suitable for my damson tree? Something eats holes int he leaves early every spring.Do you have to spray all the small branches and twigs or just the main ones?

The whole tree needs spraying, and do be careful. If the wind changes then you can get a face full of the soap and it ain't pleasant.
Be nice if we ever got a still day here, the wind blows every day of the year.

Will go get some and wait for the weather!

In parts of Europe and the Americas they paint trees with special white paint. It is mainly to protect fruit trees from the weather but also seals in bark and stops Codling moths from breeding. Something to consider and would make a feature.

Thanks B, if you know the name of the paint let me have it please.