Elicia Willis on Facebook - she's based out of a storage space in Merton. She's a member of SW18 mums FB group if you can't contact her otherwise. I have used her twice for buggy repairs and she was super knowledgeable and reasonably priced.
Also a guy called James Rainey, he is closer by and might be able to pick up and drop off your buggy. He again is a member of SW11 network and SW18 mums on FB, he contacted me regarding a buggy repair I was looking for, I did not use him so can't comment.