As you can see in the below chart, 205/45R16 has a higher standard load index than the standard A2 tyre sizes. This means that 205/45R16 tyres don't need as much air pressure as the standard tyre sizes.
Standard Load Index
175/60R15 81(462kg)
185/50R16 81(462kg)
205/40R17 80(450kg)
205/45R16 83(487kg)
For "town driving with two passengers and little load". I would try 32psi front/29psi rear, and then a slightly softer 29psi front/26psi rear.
However, adding two or three rear passenger and perhaps some heavy luggage in the back of the car, requires a big increase in tyre pressure...at least if you are going to be driving at high speed.
So 29psi front and 26psi rear could become 32psi front and 35psi rear when a lot of weight is added in the back.
For 205/40R17 tyres, a heavily loaded car might have 35psi front and 38psi rear. This allows the front tyres to support a weight of 720kg, and the rear tyres to support a weight of 780kg, ie. a total weight of 1,500kg.
According to wikipedia, the maximum kerb weight of the A2 is 1,030kg. So tyres that are inflated to support up to 1,500kg, provides for up to 470kg of load. If you had five passengers including driver weighing 75kg each, that's 375kg. So that 470kg is looking like plenty of tyre pressure for adding some luggage in the back as well.
Minimum tyre pressures are based on maths.
Maximum tyre pressures are based on owner's preference. Over-inflating tyres makes the ride harder. Although higher tyre pressures can make the steering and handling sharper. However, even on tyrereviews where they spend much of their time trying to shave one second off their lap times while testing around a race track, I doubt they over-inflate much.