Haematological quality and age of donor blood issued for paediatric transfusion to four hospitals in sub‐Saharan Africa by Uyoga, S, Mpoya, A, Olupot-Olupot, P, Kiguli, S, Opoka, R, Engoru, C, Mallewa, M, Kennedy, N, M'Biya, B, Kyeyune, D, Wabwire, B, Bates, I, Gibb, DM, Walker, AS, George, E, Williams, T, Maitland, K