How big is your space? U-shaped kitchens don't usually lend themselves to an island.

You need a minimum clearance of 36" for each walkway; 42" is preferred, 48" if there are multiple cooks in the kitchen. If you want seating on the island, you need an overhang of 12" at a minimum, 15" is more comfortable. With seating, you need a minimum of 42" clearance for a walkway behind the seating. Also, take into account that your counters will have a 1.5" overhang from your cabinet size.

(Pros, have I got this right? I've been learning!)

Could you post a few pictures of your kitchen? If you have a measured floorplan with locations of windows, doors and appliances, you would get better advice.

Whether or not an island will fit in your kitchen and allow adequate space between the island and perimeter cabinets, depends on the size of your kitchen. A u-shaped kitchen that is 10x10, for example, will have approximately 6 feet of floor space between the legs of the U (subtracting out 24 inches for each leg of the U). Sure you could fit a cart or utility table in the U but maneuverability would be limited.

Assume you want nice wide 48-inch aisles. The kitchen would need to be at least 12 feet plus whatever dimension island you want. That means if your kitchen is 14 feet wide, you would only be able to fit a 2-foot wide island. These are design guidelines, of course. If you were ok with 36 inch aisles, then you could go with a larger island of 4 feet in width.

You would get a lot more responses if you post a to-scale layout of your kitchen.

U shaped kitchens rarely have enough room for an island. It would have to be a honking big U to actually have room. And, putting in an island usually blocks your workpaths. Which makes it work worse, not better.

Do you have 120” on the interior of the U? Because that is what it would take for a single cabinet width 24” deep island.

If you need a "landing zone", look at the Ikea "Forhoja" island cart. It's only 17" wide an it's perfect as an extra bit of counter in a small space. My kitchen is only 11 x15 - too wide to be a galley kitchen and too narrow for a true island. This has been perfect for me! I painted the base black as I wanted it to disappear. I used mineral oil repeatedly to oil the butcher block top - it looks great. I love the drawers - they open on both sides - very handy - and the two shelves allow space for cookbooks, bath towels to dry the dog when it rains, and a caddy for the dog's meds etc. It is a great value - all wood - took DGS about 2 hours to put it together with a rubber mallet. VERY study and well built.