The image of a sunset and bird being edited on the computer by Steve Bright at 47:01 - implied to be recent and unedited - is seen framed on the wall in the next scene.
Madrigal's old-fashioned photographic business and the digital camera shop 'Quikpix' are supposed to be in two different villages, Luxton Deeping and Midsomer Market respectively. But when Madrigal is taking one of his daily photos outside his shop (at 37 mins 20 seconds), Quikpix is visible on the corner behind him.
It's common in TV shows and movies to insert the sound of a motor drive when someone takes a picture--whether a motor drive is being used or not.
When Seb is photographing his plate of bitten biscuits, he's using a camera that has no motor drive. You can easily tell, because he manually advances the film after each exposure (which defeats the purpose of having a motor drive--that's its job).
Digital cameras, of course, need no motor to transport non-existent film, but you often still hear a motor drive "squeee" anyway. I suspect it's a running gag or in-joke within the sound editing guild.
Seb is developing colour photos (incorrectly) in trays. Colour photos can only be developed in complete darkness.
Colour photos are not developed in 'trays'. The paper is exposed, then placed in lightproof drums with the chemicals. Black & White photos can be developed in trays with ambient low light.
At one one point Headley Madrigal makes the statement "No batteries" and yet his son Sebastian uses a camera with a motor drive which would be powered by batteries. Similarly, flash guns would be battery powered.
On Tom's fingerprint form (at 35 mins 35 seconds), the dabs were said to have been taken by DCI Spelman.
In the closing titles, his name is written as Spellman.