Adding topsoil /compost
After I’ve finished weeding I’m going top up the soil with compost /topsoil will I need dig over all soil in borders first
It all depends on your previous years' regime. If you have only started working on the soil this year, then I suggest you dig more deeper and turn the soil and maybe wait another week to see what other weeds may pop up and weed again. Others may suggest a different approach.
Soils that have been worked on can just have new layers of compost or top soil added in. Soils that have only been weeded lightly but never worked on in previous years should have top-soil and compost mixed in.