Source Affordable UK Used Cars

I want a steady stream of great-value used-car opportunities from across the UK. Price is the single most important metric for me, so every lead must clearly beat the prevailing market average while still passing the usual provenance checks (HPI clear, service history, no outstanding finance, etc.)... (Budget: £2 - £5 GBP, Jobs: Data Analysis, Data Collection, Data Entry, Data Scraping, Excel, Market Research, Web Scraping, Web Search)