Complex sentence: The Dispensary had moved premises to Ancoats Crescent in 1850 and when that site was bought for development by the Midland Railway in 1869, the facilities relocated to 94 Mill Street (now Old Mill Street).
Split into simpler sentences: The Dispensary had moved premises to Ancoats Crescent in 1850. When that site was bought for development by the Midland Railway in 1869, the Dispensary relocated to 94 Mill Street (now Old Mill Street).