I'm looking for a grand piano under €8000 and I wondered if anyone had some advice as to be how best to find one. I'd prefer a German instrument but would consider anything - condition is more important. So far, my internet searching has not been very successful.

I only know enough about pianos to tell you that your chances of finding a good grand in decent condition for 8,000 euros are nil. You might get a decent used upright for that money, but forget about getting a grand altogether, unless you only want something that looks impressive, and don't care what it sounds like.

Was also asking myself if you want a new one or if a used one is OK.
It's also not clear to me if you have contacted suppliers already, and they could not offer what you want, or if you didn't find any suppliers at all.

I don't know anything about pianos, so don't have a first hand recommendation, but this is one of the first that came up when I googled "Flügel Hamburg":
Klavier Knauer
I remember coming across a place in Altona, with a grand piano on the roof, not sure if this is the same one though... will try and find out more.
edit: that is the one, it's on a photo on their website.
Apparently they are well known and have been in the business for quite a while...

I just did a google search, using "hamburg Flügel anzeigen" and got quite a few hits. Also look to the right side of the window where there are sponsored ads.

For example, Pianohaus Zechlin Große Straße 6a * 22926 Ahrensburg bei Hamburg
If you look on their web site under Gebraughte Flügel, there's one going for 4800 euros and they say "Guter Zustand. Werkstattgeprüft. Zechlin-Garantie."

Here's a Yamaha grand, going for 5790 euros

I also found a place called PianoHaus Huster in Hamburg. They aren't currently showing any used grand pianos on their web site, but you never know what they might actually have, so might be worth a call.

I would also use the yellow pages for Hamburg and just call around some places that deal in used grand pianos. Even if they don't have anything at the moment, they will know that you are interested and will call if something comes in that suits your requirements.

I bought a piano recently from Pianohaus Hamann. Dorotheenstr. 116-118 Tel 040 420 22 11 22301 (nearest U-Bahn U3 Sierichstr.). I was very happy with the service and they sell new and used instruments.

Good luck.

Eve