I think volunteers are great, but if they pop up in a place that will significantly affect your other plantings, I'd consider them more of a weed (plant in the wrong place) and remove or move it. Especially if it's an allelopathic plant like black walnut.
If the fence and the pear are to the north, and you're in the northern hemisphere, is the shade coming from the two houses?
"Hundreds of years from now it will not matter what my bank account was, the sort of house I lived in or the type of car I drove... But the world may be different because I did something so bafflingly crazy that it becomes a tourist destination"
Hmm, I know nothing of currents or gooseberries.
Do they take a lot of pruning?
Sour cherries would be amazing, but how big do they get?
I'm not scared of roots, but I don't want a wide tree
The houses are about 10 feet apart.
The bed is against one house and the fence, on the other side of the bed is a 2 foot wide path and then the second house.
The pear is about 3 feet from the fence, and it has another black walnut sapling growing two feet in front of it!
I planted the pear, rescued from the end of the year sale, knowing it was a poor location, but not have a better choice at the time.
It had thrived, but the location means it mostly fruits up high, presumably because that where it gets sun.
I have been unable to bring myself to prune it in any serious way, but that is another topic.
The bed is inconveniently placed, but very rich,having been a much peed upon compost pile for a couple of years.
I have considered tearing it down and moving the soil, but that seems like waste of good ecology.
I'm amazed the sapling grew there but that is what gives me hope for anything else.
I have considered planting comfrey, and coppicing the saplings for poles.