@SarahAndQuack I can commiserate with your flooding problem. Here's what we did, in case its of help to you.
We are adjoining a farmer's field that he uses for grazing cattle, historically it was all his land and he sold half the field and the property to our predecessor. it's on quite a gradient with a stock fence dividing our land from his.
The successive wet winters have been a nightmare even with the underground irrigation put in by the previous owners, with gulleys and soakaway. They unfortunately missed out the run off from the field!.
So last year we got a surfacing company with their heavy plant and equipment to dig a trench the length of the stock fence and back filled the trench with hard-core and gravel then top dressed with the soil from the trench. It has by no means totally fixed the run off(King Canute and tides spring to mind!) but it has made a massive difference because our lower down borders don't flood, the water doesn't quite get there now it soaks away the volume in the French drain.
We also have a willow tree up top which loves the water so everyone's happy 😊
We needed the farmer's cooperation for access but no problem there. It cost us around £3k but it has also solved the hazard of the flooding on the drive and pathways so it was worth the investment.