Not as long as you have to wait for walnuts. I bought about a 3rd year mulberry tree, and within about 4 years I was getting enough to do a bit with them, even make a couple of little pots of jam. The main problem is picking the fruit, they tend to be inside the leaf canopy, high up, and you have to compete with wasps.

You are clearly in a fairly warm corner of the country if you think you can get something off a loquat tree. I was in Sardinia earlier this year and a lot of their loquat trees had lost their fruit to the weather this year.

Have you considered feijoas?

You'll have no trouble with asian pear, I've got one of those and when it decides to fruit they are delicious (lost the pear crop to a late frost this year), albeit small.

Cornus kousa is one of the most delicious things in my garden, and you can grow that in the ornamental area of your garden.

I read this about pecan: "It is not really a practical proposition for the backyards of temperate food gardeners, unless you are a plant experimenter with a very big lot and who likes to try to push the boundaries." They are certainly hardy enough, but seem to be cultivated in places like Georgia and Texas which have long hot summers, so I wonder whether you'll get worthwhile fruit off a very large spreading tree.

What about saskatoons/juneberries? They are delicious. Need a moist soil for them to do well. The ones which are improved for their flowering potential are not always good for eating though. I have an Amelanchier alnifolia which is improved for ornamental reasons, and the berries are disappointing.

I read this about pitanga. "The Surinam cherry is adapted to tropical and subtropical regions. In the Philippines, it thrives from sea-level to 3,300 ft (1,000 m); in Guatemala, up to 6,000 ft (1,800 m). Young plants are damaged by temperatures below 28º F (-2.22º C), but well-established plants have suffered only superficial injury at 22º F (-5.56º C). The plant revels in full sun." "The first Surinam cherry was introduced into coastal Israel in 1922 and aroused considerable interest because it produced fruit in May when other fruits are scarce, and it requires so little care; but over 10 years of observation, the yields recorded were disappointingly small." So maybe you can keep it alive in a mild part of the country if you protect it when young, but you aren't going to get much fruit off it.

If you really are in a supermild corner of the country, you could probably grow avocado. I think some people have got them to fruit in S Devon.

As a quince grower, I've always been intrigued by pseudocydonia sinensis, which is said to be edible raw.