For a recent death, you can lookup the death indexes up to 2020 on the GRO website. It’s free to lookup but you do have to sign in. If you need the death certificate then you can order one online.
You can also do a probate search for free.
If you don’t have a subscriptions to Ancestry or FindMyPast, you can use your local library’s online resources for free. Both have varied electoral registers etc., FindMyPast also has newspapers but they are more limited for more recent dates.
Of course this becomes more difficult if you have limited knowledge of the person’s age, location etc., or they have a common name. You can also try looking up siblings to see if they or any or nephews are alive and contactable.