Indeed. I just took the top off to see how I can get the front off to get the door seal/bellows out.

Modern machine have a plastic front panel that seems to come of reasonably easily. Our machine has an all steel front section, which is bolted/screwed to the rear half of the machine (also steel) in many place (including a top bracing frame that has loads of electrics, valves etc mounted on it.

Unless there is some trick that I'm missing, getting a look at the drum would require very major disassembly (I'm wondering if the drum was inserted from below).

I can't see any disassembly details online for machines like ours.

My best guess at the moment as to what is going wrong is that it is adding way too much water. It is supposed to use ~40 litres through a whole full wash/rinse cycle.

It appears to be adding 150 litres of water to the drum during the wash cycle alone. It jets water downwards into the drum, so I'm guessing jetting the water for the whole cycle builds up loads of foam.

At this point I think I am just going to have to give in and spend £300-400 on a new machine. It doesn't seem sensible to start spending money getting someone else in to maybe repair a +15 year old machine.