Loads of data on variouus national CAA/DOT websites.
Try
www.caa.co.uk/airlinestatistics
Anyway, load factor isn't a single simple measure.
There are several ways of measuring it based on pax/seats or tonnes flown/tonnes available or weighted for loads and distance flown (RPK/RTK and ASK/ATK, with further wrinkles for combination self-loading and non-self loading traffic varieties,
What really matters is how the particular load factor measure compares with the break-even load factor calculated on the same basis.
If your load factor is 85% and your breakeven is 90% your'e stuffed.
If your breakeven is 105% your stuffed, embalmed, buried and cremated, regardless of any actual load factors.