any likely problems when replacing.refitting Euro hinges into kitchen unit?

I did that with many old cabinets before I tore the old house down. Recommend car body filler to plug the holes. A far better substrate for screws than chipboard

Hmm - I am not planning on plugging the 35mm main hole with CBF before re-drilling just a mm or so away...The old small screw holes will need to be plugged - I might use CBF, or just thin slivers of wood(*) + PVA glue.

J^n

(*) I keep old Magnum Ice Cream sticks for this kind of thing, I think they are beech or similar. Much better than matchsticks. Or, wooden stirrers from your favourite artisan coffee shop.

Yres. I found the old screw holes were substantial in diameter and nearly always pulled out, Hence CBF. If you don't redo the 35mm one the the hinge will stay in exactly the same place. Oh and the 35mm one is in the door. The bit that goes is generally in the base units which is where all the adjustment is

The 'base' (side in my case) may be where all the adjustment is, but the main hole's distance from the edge of the door is also a factor. This governs the amount of 'everhang' the door makes onto the base; and I think it may be this that is a bit out in my case. That (I think) is why my attempts to adjust have not been successful.

Some of the hinges available (better quality ones?) seem to have an extra screw in the base plate; I think this might be helpful in my situation, but if others have experience in this area I would be interested in hearing about it.

I've only seen them with two screws, but otherwise hinges do vary a bit from one to another make. They may indeed have fixing screws in different places. I think the 35mm distance from the edge of the door is standard, and they usually have quite a large range of adjustment in two directions.

I've replaced them (at 40 or more years old) because the spring mechanism has failed and they don't hold the door shut, or they make an almighty clunk when opened and don't feel right.