dublinpilot
No - no misunderstanding with the phraseology - see barshaker's post above.
I imagine that often when a controller tell you to standby, (s)he already knows if he can let you through or not,
Standby tends to come in answer to the initial call - therefore how do you know you can approve a zone transit if you don't know that's what they want? In addition traffic levels around some of the busier, Class 'D' regionals around the UK, which aren't constant, often mean you don't know whether the transit will be approved until you've fully assessed the information (distance, speed, expected traffic etc etc etc).
"G-xx remain clear of controlled airspace, and I'll be back to you in a minute with instructions for your transist" or "G-xx continue on heading, and I'll be back to you in a minute with further instructions"
Example 1 displays an assumption the aircraft wants a zone transit before they've asked for it - ATC is a game where assumption doesn't play a part.
Example 2 could never be used because if they were close to the zone boundary, and you told them to continue on their heading and got tied up with other things you leave another uncertainty factor in the cockpit "Do I continue on the heading and cross, or do I stay outside?". Also you don't give specific headings to VFR traffic unless you ask them first in case they enter IMC. inadvertantly.
As for the diversion scenario - there's nothing difficult about turning 90 degrees (if that's what's needed, it may not be that much) and then doing a quick map read v ground reference re-route to pick up your track on the other side. You don't need timings, you don't need to re-calculate, just basic map reading skills (which the PPL does learn during his course - or at least I did when I did mine, and have used when flying in unfamiliar countries, never mind areas of my own country).