I put in my fruit and nut trees abut 2 years ago. The apples and pears are being trained as espaliers along the fence line and cherries and plums/gages as a sort of hybrid espalier/fan. It does mean that they get checked in the early stages so i stuck a few extra cherries and gages in last year to just let them do their thing elsewhere for an earlier fruting start (there are some more mature apples and pears here already which I'm having to reshape and re establish from long neglect)
My mulberries are too small to need any pruning yet and the apricot/peach and almonds ar all nicely shaped and really dont need any attention at all yet - apart from my plans to spray with home mixed bordeaux end fo this month as a curl preventative. the peach gets leaf curl whereas the others have been clear so far.
My nut trees are also only couple of years planted and perhaps a bit exposed and slow to really establish as walnuts, chestnuts and cobs. the wild hazel is another matter.
I really wouldnt plan on prunign sweet chestnut or walnut unless it develops a ragged habit or when it's about 30 feet tall and threatening to fall over in the snow
Unless you want to coppice the SC for wood rather than nuts.
NOTE: I discovered that one can source pecan and hickory nuts from forst hardy canadian stock capable of tolerating below -15C so i have some seedlings in pots waiting for them to get big enough to compete in open ground. I did lose about half of them last winter when it was pretty darned cold here and they had only germinated that year. I think the remainder will be fine now. Also look at monkey puzzles as a nut source - very tolerant of british climate but like the pecans it's a venture for future generations more than for me - perhaps 25years to a meaningful crop