Just stopped starting!

[Matt6r]

Hello, My lovely smax 2.0 tdi has just gone dead!

Working one minute, then wouldn't start. 

Engine turns over but doesn't fire up. 

Checked the cam belt, fuel pump fuse and relay and inspected fuel lines as best I can. 

Things I note are;

1. A lot of air in the fuel pipe as it exits the right of the fuel filter? This connector feels a bit loose and wobbly!

2. With the ignition on, the high pressure pump has that whinning noise that I assume is the initial prime, then it clicks off. This makes a high pitched noise constantly?

Does all this sound like the in tank fuel pump?

What checks can I carry out now?

Thank you for any advice.

Regards. Matt.