The easy answer to that is, it's not really that easy nor straight forward to answer.
Assuming this "adequate monthly income", is current prices rather than pre cost of living because my electric bill cost £22 for 10 days as it is and that's with enforced rationing!
Furthermore, does this then run the risk of being deemed ineligible for further financial top ups with student loans, free school meals, free school bus pass, free dental, prescriptions, vouchers towards glasses, school trust funds, bursaries, council tax and housing benefit support and cost of living payments etc etc?
Ideally I'd like to have enough to pay for our own home, a reliable car, and be able to pay into a pension for when I am old and grey. Least a week's holiday away each year, would be good, plus eating out regularly and able to buy tickets for shows or concerts occasionally or a new wardrobe from time to time and salon appointments.
Obviously it would be helpful to have savings for a rainy day or to leave a lumpsum to my family (something very much frowned upon by the DWP for benefit claimants) when I pass away.
This is all a pipe dream of course.
Without context, and in addition to the financial support we also receive at this time £25,000 to £26,000 would seem reasonable to cover things as they are, without being too greedy.
But then as the saying goes, "Greed is a bottomless pit"....Erich Fromm