ONS Retail Sales Value NSA
The Retail Sales Index (RSI) (value, non-seasonally adjusted) measures the value of retail sales in Great Britain on a monthly basis and does not adjust for seasonal variations (e.g. the timing of Easter). The value estimates reflect the total turnover that businesses have collected over a standard period, expressed as annual percentage growth compared with the same month in the previous year.
Office for National Statistics
Retail Sales Index
Subscribers can download 10 years' worth of data.