There is a someone in Middlesbrough who breeds black and white Basenji. He has not bred this year though. Someone who owns a sibling of my 8 month old puppy also has an older black and white puppy from him. https://alchez.weebly.com/#
Whereabouts in the South East are you? I am in Medway.
You are far too late for puppies in UK this year - all are about to leave the nest or have already been rehomed. If you email me privately I will send you a list of breed club secretaries and you can explore and maybe get onto a waiting list for some year in the future.
Lists for next winter are already filling up, demand is far outstripping possible supply.