I basically wait until everything else is in and then inter-plant them with stuff I know they won't grow over - mainly my beans and sweetcorn - it's kind of a messy 'three-sisters' method but always works out ok - I generally plant about 10-12 plants but always about 2-3 foot apart...
That is what I do as well. I have a large fenced area on the plot (muntjac deer problems) and I have a mix of planting beds and paths. The squash are destined for the top end on this planted around other stuff. I train the foliage down the edges of the fence and around the other stuff and let them roam a bit. When I say train, that consists of me picking up and moving tendrils around areas I want them to keep off and into bits they can creep across freely.
The other stuff they grow around are tomatoes, sweetcorn and beans, so mine is messy 2 sisters, plus a cousin or 2
60cm spacing is not really practical. Even a non trailing bush type courgette would be hard to contain within that. You could cram plants into a small bed that close, but you would need a large clear area around it for the foliage.
