There is a site called Author Ad Network that will charge US$129 to submit your bargain or free book to 28 sites. But what about a free list? That might help to make an ROI on this idea.

Free Places to List .99 cent, 1.99, or 1 pound deals 

Master Submission List: https://blog.reedsy.com/book-promotion-services/?

Tick ‘show only free sites’

BookAngel

http://bookangel.co.uk/

Tried to List – but as my ebook listed is in USD, it’s not under 1 pound!

BookDoggy 

Mostly amateur fiction

Free and 99 cents, very few $1.99

Indie Book Lounge

http://indiebooklounge.com/

Extra dodgy-looking website. ??

Ebook Stage

https://www.ebookstage.com/

Can sign up for affiliate program to earn points for deals, add author profile, and add book deal.  Don’t want to promote? Pay US$10 for one book deal promoted to their readership and Twitter. Tested, no results.  

Goodreads Giveaway

This is different, it is giving away a copy of print or eBook to interested readers… and it’s no longer free.

https://www.goodreads.com/giveaway/show_create_options

Basic giveaway costs US$119 to run but Goodreads added things to help the promotion. Winners get a prompting to have the winner review the book. The recipients get the book in their ‘reading’ list.

Lots of Other Places to Submit Books

This Awesome Gang (and their list) has the most positive testimonies (US$10 to upgrade to their social media lists):