Jimlad,
The normal maximum range scale for the H2S was 1:1 mil. 543 had a modified Indicator 301 with a 1:2 mil scale. I don't believe it actually changed the maximum range of about 160 miles.
The picture was verbally told back to base or 3rd party if required but not every time, it all depended. It was Operation Instow.
One method was to create a surface plot using the H2S and nav system with the plotter plotting contacts. Every 15 minutes the plot was 'told' back on HF. In high density situations, such as the Med, it could be very busy. In the Indian Ocean, with only 2 contacts in a hour, we could spend more time actually searching.
The plot was told with reference to a reference point and cartesian coordinates. It was possible to classify contacts as small, medium or large.
How this differed from the Nimrod is that the Vulcan would fly at 40000 feet with a radar optimised for high level operations. The Nimrod would also conduct a surface plot and could then visually identify what it found. Range considerations generally restricted the Vulcan to high level but it was also considerably faster than the Nimrod.
The Nimrod OTOH could use its ARAR/ARAX to identify emitters and aid identification of radar contacts.