The Santaram laundrette on Brockley Rise is still open.
13 Brockley Rise, Forest Hill, London SE23 1JG
Near the junction of Stanstead Road and Cranston Rd/Brockley Rise.
I have to warn yout that while some of the people who work there are lovely, one is actively unpleasant, pretty much all the time and to everyone. Also, don't believe the advertised times. They seem to be doing 8-5 currently. They were still open on Sunday but the owner is keeping it under review - depends how much people are using it (less than before the lockdown in my experience).