There are a range of businesses that offer film printing services ranging from disposable cameras to high end exhibition printing, this can be done on the high street or from an order services.
The basic services offer by high street chains like Boots and Tesco include photo printing from either or film or digital media and personalised printed gifts. This type of printing service would be useful when you need low quality prints for personal use.
Darkroom printing can be done to change a piece of film to make them images look how you want personally, film can be changed in a range of ways in a darkroom from changing the size of the images, adding contrast and cropping the images. You would use this more for small personal projects where duplicate prints are not needed or experimenting with different ideas and techniques.
Highstreet photographic specialists offer a range of high quality professional printing services as well as photographic themed products. They can also batch print images with specific instruction like certain effects or sizes. This would be most effective when high quality prints are needed for personal projects or for small exhibitions.
Professional Printers like metro prints in London these offer a large range or printing services from super high quality canvas prints to extremely large prints. These types of prints would be used for national gallery or for one of pieces of art made by professionals.