https://www.gov.uk/government/statistical-data-sets/price-paid-data-downloads

The size is about 4 GiB uncompressed:
http://prod.publicdata.landregistry.gov.uk.s3-website-eu-west-1.amazonaws.com/pp-complete.csv

Redistribution is permitted with attribution.

Description of the fields: https://www.gov.uk/guidance/about-the-price-paid-data