Was 100 shillings a lot in the early 20th century?
This may help. A pound of bread in 1912 Britain was 1.3 pennies. A loaf of bread (in the U.S.) is usually ~ one and one quarter pounds, so figure maybe two pennies for a loaf of bread in 1912 Britain (if their loaves are similar). There were 12 pennies in a shilling, so 100 shillings would be 1200 pennies. That would buy 600 loaves of bread. Then you have to figure housing costs, clothing, heating, and so on. The Victorian source below may be useful for you.
Sure was – there were 20 shillings to one pound [English] so that 100 shillings = £5. In the early 20th century wages were quite low and the average worker pre-World War One, would not have earned more than about £1.50 [30 shillings] a week. Yup, a fiver was big money back then. Come to think of it a fiver was big money when I started in the Army aged 15 back in 1957 when my weekly pay was thirty shillings or £1.50 in modern money. Just about the price of a cup of coffee here in London now, but back then a whole week of entertainment, including the movies for about 15pence [equivalent]. And a cup of tea back then [1957] cost about 2p – blimey! 1941 model….