Cycling Techniques

I get the theory about having eye contact, but find it difficult to do so in practice (moving traffic).

When are you suppose to attempt to get eye contact? When attempting to do maneuvers such as moving out to pass parked cars, junctions etc. or each and every time you take backward glances?

When is it there (if ever) no point in making eye contact when driving alongside moving traffic?

Great point.
Off the top of my head it is most important whilst moving and wanting to switch lanes. You don't want to try and switch lanes in moving traffic without knowing for sure if the vehicle behind isn't about to go speeding into the space that your attempting to get into- it is the surest way of knowing whether you have been given way OR NOT. Most other look backs are just for clarification as to what is there.
I imagine multi lane roads, navigation on larger roundabouts **AND **right turns are heavily reliant on proper eye contact.

If this doesn't make sense I can clarify it better.