How do I Get A List of 300 UK Guest Blogs?

I need up to 300 Guest Blogs in UK With at least 5k Monthly Organic Visitors.

My company is launching by Oct. And we want to start publishing content to create a brand awareness. How do you think i can get this guest blogs in UK?

I have checked Fiverr, many sellers there don't have UK Guest blog with UK Audience.

At least the sites should have 40% of UK Audience.

I need your idea