135 film comes in different exposure sizes: 12, 24, 26, 39. The cost is the same regardless of the number of exposures taken. It is impossible to tell once the film is out of the camera if it has been used.
Develop, scan and upload to WeTransfer: £7.99 per film
Develop and print to 4″ (w): £10.99 per film
Develop, print and upload to WeTransfer: £11.99 per film
The order form has all the details and services together with a postage label.