C# - I need a simple application that simulate the behavior of a vending machine.

General information for the business: Write the application as easy as possible, but it must work.
Kind of development: New program from scratch
Num. of modules: 1
Description of every module: The program must simulate the interaction with the user (e.g. prompt for coin value rather than talk to real hardware) but please assume that the result is intended for a real life scenario. The program must provide the user an interface that provides the following features:
Presents a list of the available products including available stock, price and product name.
Enables the user to select a product.
Prompts the user to insert coins to pay for the product.
Once paid for, returns change (if applicable & can just be printed values) obeying the rules of the currency, e.g. only return £2, £1, 50p, 20p, 10p and 5p coins. 1p and 2p coins need not be supported.
Stock values must be kept up to date.
Validates user input, e.g. coin type, product is in stock, etc…
The task is open ended.

For clarity, two screenshots of a working example are provided in the document attached.
Description of requirements/functionality: Please implement your solution in C#. You may implement a GUI, but I recommend a simple CLI interface. When designing and writing your solution, please keep in mind:
Good OO design principles
DRY
Separation of concerns
Potential future expansions or requirements changes
Use of dependency injection
Simple Unit Tests
Extra notes: