Travel to Zambia.
British Airways fly direct London to Lusaka. Another BA route to consider is London, Jo’burgh (RSA) and then get another airline to Lusaka.

Ethiopian airlines, flying London, Rome, Addis Abbaba, Lusaka.
They are proving to be quite inexpensive but there is a few hours to wait in Addis Ababa airport.

KLM also do flights to Zambia. Missionary discounts available through Siama travel company. Siama web site.

Within Zambia.

Useful help with flights and guest accommodation can be gained on the CMML Flight Service website: cmmlflightservice.com