The time to pick them is when the calyx (the bit surrounding the nut) begins to turn yellow. If you pick them too soon, they do not ripen properly and too late, they fall out and get eaten. Squirrels and mice take them round here.
Our hedgerows are full of the trees, but they hedge cut at the wrong time of year so all the flowers (catkins in Feb/March) which appear on new wood, are removed.
Pruning is easy, remove about a third of the branches anytime from now on.
This part of thwe West midlands has the coldest recorded temperatures in England and they survive here. Fruiting is erratic though, they do not like the icy winds we get at pollen time. If in doubt, why not plant some of the bought nuts and grow your own? That way you lose only time rather than money!