I have bad experiences with mister-auto and many german part web shops.
Recently i ordered a radiator from mister-auto. Website says that it was in stock. It turned out it was not in stock.
But i have to say that i got my money back quickly without much hassle.
Some time ago i was looking for a steering rack. It was listed on many german web shops. All these web shops says it was in stock, and inmediatly available. But after ordering and paying, it turned out the part was not available. Getting my money back was a pain. I had to start a pay pal claim to get my money back.
I emailed all the other web shops who its website says it is in stock. Some webshops did answer, some not.
The website who didn't answer, i ordered the part without paying, to force them to tell me the part is in stock or not.
It turned out no webshop could get me the steering rack.
Some days later i looked again, and all those website were still saying it is in stock
I learned not to thrust the statement "in stock", and make contact to double check.
All you say, Bart, is true of nearly everyone on the internet these days! It is one of the worst things about internet shopping. My system is to email them and ask first. Any company that cannot even be bothered to reply, I will not do business with anyway. If they can't reply to an enquiry it is more than likely they will be a pain to deal with over any later issue.
In the case of Mister-Auto, they have always replied to my emails quickly - usually within the day, and if you did order something not in stock, and paid with a credit card, the money is refunded straight away with no action required.
However, they do stock parts that many others don't appear to have and I have had some bargains too.
As with all purchases off the internet, particularly for rare old cars like ours, you have to take steps to protect yourself and only pay if you know they have stock; or deal with someone who will not take the money until the parts are being despatched or return your money immediately if it is found they are not available or there is any fault which means you need to return the item. I have always had excellent service for example from Amazon, so they get repeat business. I do not deal with eBay or have a paypal account as I don't find either company reputable.
Roy