AEG Favorit 5040 Water Level control query

My AEG 5040 dishwasher main wash circulation pump has failed as a result of ingress of water into the bearing causing seizure. Before spending £150 on a replacement, I sought to check there was nothing else adrift. The machine is basically very clean, having had limited use. The water matrix is clean. There is no evidence of fat etc in any tubes. Heater is OK, and timer believed to be OK, but I am suspicious about the control of water level. The machine does not fill above the level of the filter. I assume it should.

I have checked this on both the prewash and main wash cycles, with the seized wash motor disconnected, and precautions taken to prevent damage to the heater, which, as a result of lack of fill, is not immersed in water. I am assuming it should be. When the machine pumps out the only volume which empties is that of the sump.

I am quite happy to fork out to replace the pressure stat (£20 odd) as well as the wash motor, but before doing so would want to understand:

1. What level should the machine fill to? Is the level the same for the prewash, main wash and rinses?

2. Is the pressure stat the only element which controls water level in this machine, or are there other controls which might be at fault?

I believe in keeping solid older machines going, but before spending £170, I want to be confident that I have not got some other fault, through failing to understand how water level is controlled in this model. The PNC number is 911 232 040 01, Serial number 94701242, and it is a Typ 45CEL03.

I will be very grateful for guidance. Many thanks. Ian