Greg Davis' thread on film-washing tests tells the tale superbly. I suggest reading it if you haven't:
https://www.photrio.com/forum/threads/film-washing-test.69416/ You can use the data here to determine a method and wash time that works for you if you don't want to test yourself.
Bottom line: a wash aid will help with film wash times if that's important for you. It's not necessary if you extend wash times accordingly.
Testing with the HT-2 test is fairly easy and gives a lot of peace of mind. If you have any questions about the efficacy of your washing regime, test. Adding a bit more time to any regime won't hurt, nor will it use appreciably more water. I like safety factors.
FWIW, sulfite-based wash aids can reduce the stain from staining developers like PMK according to Gordon Hutchens, author of "The Book of Pyro." For that reason, I don't use wash aids for film. However, I wash appropriately longer. My standard is 30 minutes in a Gravity Works washer that fills and dumps through siphon action. It's a water-waster if it runs the whole time, so I run a couple of fill-and-dump cycles, turn off the water flow and let the film soak for five minutes or so, run a couple more cycles and soak some more, finishing with three or four fill/dump cycles. My film tests fine with the HT-2 test for residual hypo.
I agree that saving water is important, especially in areas where water is in short supply (thankfully not here in Eugene, OR). However, how much does two or three extra liters of water cost? And how often do you process? The cost for extra water may be negligible if you don't process that often or process in batches. One toilet flush's worth of water will likely wash several rolls of film

(Come to think of it, the toilet tank is a fill-and-dump system... Perhaps one could combine tasks...)
As for the Ilford method: I've never tested it. If I were to use it, I'd definitely do an HT-2 test the first few times to ensure it's doing it's job. AFAIK, Ilford assumes a wash-aid step in their sequence. Without that, soak times and volume would have to be higher.
Best,
Doremus