Now comes the doubt, the check altitudes, on the other hand, will be affected by the temperature, and I will expect to cross them lower than mentioned on the chart, even if I am on the G/S? Can I assume that terrain clearance is guaranteed as I am following the G/S?
A quick rule of thumb: A pressure altimeter will under/over read by c.4% per 10deg C deviation from ISA. That 4% applies to the height of the aircraft over where the pressure setting for the sub scale was derived.
On an ILS at a fixed distance, warmer than ISA, the altimeter will read less than the check altitude/height and colder it will read more.
Edit: crossed with Goldenrivett: I agree.