A bunch of really random price drops at Kindle UK, some quite nice IMO...
Walter Mosley, all £1.99 each
Always Outnumbered, Always Outgunned, Socrates Fortlow #1:
https://www.amazon.co.uk/dp/B07BF6GF55
All I Did Was Shoot My Man, Leonid McGill #4:
https://www.amazon.co.uk/gp/product/B007C52KYK/
And Sometimes I Wonder About You, Leonid McGill #5:
https://www.amazon.co.uk/dp/B00PW634P0
Steven Saylor
Rubicon, Gordianus the Finder #7, £1.99:
https://www.amazon.co.uk/dp/B005QMUTAS
one of the earliest historical series I read and liked
Erle Stanley Gardner (& pen name AA Fair)
a whole bunch of titles at £0.99/£1.99 each, mostly Bertha Cool/Donald Lam, link for all (with a few strays):
http://www.amazon.co.uk/gp/search/?s...price-asc-rank
Alan Hunter
Gently Where She Lay, Inspector George Gently #19, £1.99:
https://www.amazon.co.uk/dp/B00ET3NP2Y
Peter Lovesey
Bertie And The Crime Of Passion, third in Lovesey's series featuring Albert Edward (Bertie), Prince of Wales, £1.99:
https://www.amazon.co.uk/dp/B008MNQ948
I've quite enjoyed this short three-book series, and the first two are long-term-ish at £1.99
Bertie and the Tinman, #1:
https://www.amazon.co.uk/gp/product/B00DRI0LTC/
Bertie and the Seven Bodies, #2:
https://www.amazon.co.uk/gp/product/B00DRI0MLE/
Laura Joh Rowland
The Concubine's Tattoo, Sano Ichiro #4, £0.99, I've quite liked this series too:
https://www.amazon.co.uk/dp/B0042RU4HQ
Elizabeth Peters
Lord of the Silent, Amelia Peabody #13, £0.99, a bit unusual for later titles in this series to go on sale this low:
https://www.amazon.co.uk/dp/B0080K3KF4
Jonathan Gash
The Great California Game, Lovejoy #14, £0.99:
https://www.amazon.co.uk/dp/B06XRKVMSW
Paid and Loving Eyes, Lovejoy #16, £0.99:
https://www.amazon.co.uk/gp/product/B06XRK9CKB/
Jade Woman, Lovejoy #12, £1.99:
https://www.amazon.co.uk/dp/B06XR1R5YN
Moonspender, Lovejoy #11, £1.99:
https://www.amazon.co.uk/gp/product/B06Y5SS1HX/
Also a series I've liked a lot...
James Patterson
Cradle and All, non-series, £0.99:
https://www.amazon.co.uk/dp/B0053YQMOG
Simon Brett
The Body on the Beach, Fethering #1, £0.99:
https://www.amazon.co.uk/dp/B07L6FK9H1
Yet one more fun series that I've liked.