Complex sentence: The first 13 years were spent at 29 Great George Street, Westminster, and the collection increased in size from 57 to 208 items, and the number of visitors from 5,300 to 34,500.
Split into simpler sentences: The first 13 years were spent at 29 Great George Street, Westminster. There, the collection increased in size from 57 to 208 items, and the number of visitors from 5,300 to 34,500.