I'm looking to run two sites off one Sitecore install.
The first site will only be in UK English therefore I won't include the language in the file path. languageEmbedding=never
The second site will be in multiple languages and I need to include the language in the file path. languageEmbedding=always
Is there a way I can define multiple link managers and configure the sites to use a specific link manager?
Nope, not by default. But the LinkManager is overrideable. Probably you can change the behavior by selecting a different config per site and coding this into an overriden LinkManager.
I've found the best way was to create a custom link manager that supports both scenarios. Then have a supporting config setting which defines whether the language is embedded.