Nucleon and cluster transfer probabilities have been measured in the collisions of 16,18O, 19F with 204,208Pb, 209Bi for charge stripping channels down to ΔZ = - 3. Strong evidence of correlated nucleon transfer has been observed in particular channels, and neighbouring systems are seen to differ significantly in their behaviour. New measurements were made using an improved ΔE-E telescope. The back-scattered projectilelike fragments were measured in the telescope at θlab = 160.6°, and in combination with monitor detectors at forward angles allowed determination of absolute transfer probabilities. The improved design allows isotopic yields to be measured with greater precision.