So, it appears that things have finally panned out, more or less. I've booked a hotel and a train ticket.
The train ticket ended up being more expensive as what I had read as return trip was actually only the price for a one-way ticket. Confusing, since some of the fares were only available if you bought a round-trip ticket.
However, due to a train accident (which I don't remember hearing about, but then, we have no television so my news coverage is often spotty), they're apparently inspecting all sleeper carriages and so only have Liegewagen (sleeperettes? couchettes?). And despite what the website says, they apparently only have 6-bunk compartments, but 4-bunk ones. However, there's a special price for a bunk in a 6-bunk couchette compartment, which ended up being about what I'd thought the whole trip would cost in a 2-bed compartment with real beds.
Must get around to preparing the presentation, then :)
(Oh, and pity I won't be able to take part at this year's p5p dinner--I see that they've planned that for the Saturday after the conference, and I'll already be back home then, since I'm not going by plane, which usually tends to keep you somewhere over the Saturday/Sunday night in order to get a decent fare.)