Yes i think duration and food endurance is a big and key concern. A 3 year comfort period is definately a good place to be.
In my opinion a good selection of food from across the spectrum would always ensure redundancy and robustness. Especially if you know what to forage for too.... Personally i can only accomodate for a 90 day period and am fully stocked... But it's more than just food; there are a whole load of other aspects out there from Water security (although not a problem in Wales) to defence and medications... Either way, you are definately in a good situation....
Good job!