The tyre pressure for 225 55 17 size tyre should be somewhere between 38 and 40 PSI depending on load.

205/55/16 95H = 2.3 BAR / 33 PSI
225/55/17 = 2.6 BAR / 38 PSI

SPACE SAVER (Skinny Spare Wheel) = 4.2 Bar / 61 PSI

2.1 BAR / 31PSI
2.2 BAR / 32 PSI
2.3 BAR / 33 PSI
2.4 BAR / 35 PSI
2.5 BAR / 37 PSI
2.6 BAR / 38 PSI

Will update this with more information 

Which pressure for a full load and unladen?

My Tyres are 205/65R 16 95H
I'm guessing about 33 psi maybe a bad more in the front as its front heavy.
I bought the manual off amazon and it basically says "check tyre pressure by inspecting the state of the tyres where they touch the ground"
with three little pictures of tyres!!!

So that was about as much use as a chocolate fireguard.