Is the trip meter, and reset button, another function that has been discontinued on the MK iv or is it something else hidden in the infotainment jungle?

Yes, both.

 

The trip meter as we knew it has gone, but it is there in some form - the driving data : Since Start, Since Refuel, Long-term. They can be reset on demand depending on the need (except since refuel). The Since Start automatically resets itself after about 2 hours of the car being turned off and the Long-Term automatically after 99hr 59min or (I think) the equivalent of 9999Km.

 

Can be displayed on the Virtual Cockpit ( the dashboard of old) or one of the Infotainment screens. Initially, I missed the trip meter but not any more. What's there is more than enough for my needs, and proved useful on a four week road-trip to Tuscany last year.

Still rubbish tho, the long term one resets all the time, I would of wanted the data collected from the start 0000 miles ...

 

What is also annoying is if you have the Hybrid you cant see how many battery miles you have done, just the total where as the Audi system allows you to see battery, engine and combined