Tersie,
I don't have the answer to your question other than the estate agent is the only option currently on the table, but if you would like to open a launderette in Forest Hill there are a number of other units that might have lower rents but would be perfect for a launderette, just look at the remaining empty shops on Dartmouth Road. If you would like the details of the landlords Richard from the Forest Hill Society, and the SEE3 team have many useful contacts.