Grandad, There’s a Head on the Beach is the second book in the Jimm Juree series by Colin Cotterill, who is perhaps better known for his Dr. Siri Paiboun series. It’s on sale for $0.99 in the US. Note that there are two different versions of this, from different publishers, so make sure to use the links below, and check the price before you buy.
The Motion Picture Teller is a recent (2023) non-series title by Colin Cotterill. It’s on sale in the US and UK, and discountable at Kobo UK. I’ve not read this one, but have liked a couple of his other series.
Kindle US, $1.99: https://www.amazon.com/dp/B09Y53R3TB
Kobo US. $1.99: https://www.kobo.com/us/en/ebook/the-motion-picture-teller
Kindle UK, £0.81: https://www.amazon.co.uk/dp/B09Y53R3TB
Kobo US, £0.99, discountable: https://www.kobo.com/gb/en/ebook/the-motion-picture-teller