Well I bit the bullet today and went and brought a Ehiem Pro 3 600. Had to wait a week for the shop to get fresh stock after the Christmas/New year break. I like to buy from a shop rather than the net. If anything should go bandit it's so much easier to sort. Plus, of course, your local aquarium supplier needs your support and you need your local aquarium supplier.
Have heard nothing back from Hagen.
The conversation when I made my purchase went like this:
Shopkeeper: "what ho?"
Me: "Did you put a Pro 3 600 aside for me?"
"Certainty did Fella. That'll be 200 notes please. Are you sure you need a 600? What are you running now?"
"406. Had all sorts of problems. Have you had any experience of them?"
"Won't have *insert expletive of choice* Fluval in my shop. No end of aggro. Can't get any parts. when you can get parts they cost stupid money" (his words not mine).
"You have parts for this one?"
"Got a full range of parts in stock. You won't be needing them though. Not unless you manage to break something."
200 down. 1 filter up. Hay ho.
The parts situation in The States may be different. But over here they are rarer than rocking horse poo.
Will keep you posted.