David-"If you read 714.411.202 you will also see that disconnection times of 5 sec are expected for street furniture" only if fed from highway power supplies.

"premises does not mean buildings, it is an area of land owned by a person." Agreed- but the phrase "within domestic (household) premises" does suggest inside the buildings, and, i also agree, could be better worded. 

"Gardens and drives are actually private, not public areas" but I believe only if access is fettered, eg, a locked gate, and a fence, although I don't profess to be an expert on land laws.

"You will see in 714.1 that Gardens are obviously Public Gardens, along with all the other Public spaces." but it doesn't say this, it just says gardens. It also says car parks whether or not they are private, or whether they are shut at night.

"None of this is either consistent or makes much sense" Absolutely agree.

You have not answered the question I asked: basically why is a garden (domestic) light any different from a lamp post in the street? If a lamp post can have 5 seconds why not my garden light? Why do I need an RCD when the lamp post does not, but the bus shelter light does?

Assuming your view is not a satirical one, I am glad you agree!

garden light is fed from a final circuit. 411.3.2.2,3,4 & 5, give maximum disconnection times.

the lamp post in the street referenced in 714.411.202 is fed from highway power supplies, which I assume are distribution circuits.

As Andy says re bus shelter, also used more often in the rain, wet ground. And if it's raining near a lamp post you just want to get somewhere dry, unless you are Gene Kelly

It wasn't satirical, although after posting I could see why you thought that, i was referring to the regs.

garden light is fed from a final circuit. 411.3.2.2,3,4 & 5, give maximum disconnection times.

the lamp post in the street referenced in 714.411.202 is fed from highway power supplies, which I assume are distribution circuits.

As Andy says re bus shelter, also used more often in the rain, wet ground. And if it's raining near a lamp post you just want to get somewhere dry, unless you are Gene Kelly

It wasn't satirical, although after posting I could see why you thought that, i was referring to the regs.

unless you are Gene Kelly

or George Formby

or Lili Marlenes's boyfriend 

Though of course all 3 predate the introduction of PME earthing or RCDs, and probably the introduction of any earthing at all in some cases.
But I agree, there are not generally piles of bodies under the things in the morning, nor for that matter in the bus shelter,  I suspect a bigger driver is that in a house someone will reset the RCD smart-ish if the lights go out, while waiting for someone to come out and reset a trip for a streetlamp it could be off for days and arguably there is a safety case for having it working.
Mike