Hi Hippo,
here's an update on the repair status. Sorry it took a while. As I didn't have time I found a guy in Germany with a LR garage who worked on it. Was a bit of a mess in the beginning but seems now to have worked out well.
He first checked the cables going into the Jatco and assumed the problem to come from that. Unfortunately the spare used one he had, had exactly that failure

so he ordered a new one. Didn't work out, still more or less the same trouble.
He then changed the whole valve assy for an used spare one he had laying around and got a bit better results, but he said still not as it should be hence talked to the Jatco guys. I think after that he opened the gearbox like tacr2man on one of his ones and checked everything in there but nothing wrong. He then changed some more solenoids, which I thought might be the cause but that didn't work out either. He said they measured ones with good values, next time again not and then better and so on. To get to the ground they took off the battery compartment and checked the cables. Somewhere there one or two were defect cause they rubbed somewhere on metal and damaged somehow one for the Jatco as well. They replaced everything and now everything seems to work again. The one I changed didn't look to good but it worked he said. I think he made it a bit more professional now

.
Overall he said it cost 320Euros which I think is a good price as it included some other part he exchanged as he said was defect. It took a while but I were not in Germany anyway.
I asked him also to change the power steering pump. He said for 50-60 Euros excluding the oil. He used my 'old' Jatco oil for it.
I think that's great and would defiantly recommend that guy if anyone's got trouble trouble in central/southern Germany with his LR. He's the owner and did it more or less in his spare time as far as I understood, hence a better price.
Haven't driven it though

but think everything should be fine now. I hope I can go there soon to pick 'em up.
Thanks for all the help in here.
Regards
Matthias