Sounds busy, Jon.
Barring human rights abuse or other similar privations being performed on oneself, I happen to think that moving is one of the least fun experiences in the world, so ... Good Luck With That!
In any case, the XMB messages were just on the off-chance, and based on the assumption that that's what you'd tend to see first; if you'd prefer PMs here, also not a problem.
The 7pm invite was really an anomaly; I'd tend to be on (which hasn't been much at all since Friday) somewhere in your 10:30pm-12:30am, if at all.
One easy way (if you want to be un-lost-caused, or just some time out) might be to just eyeball the 3D3_Racing lounge for others; I'd imagine it will pick up in usage over the coming weeks. Peter's or my own lounge will also show where we are if we're running online; speaking for my own part, if I'm in my own lounge or a WRS/3D3 one, I'm available (in nearly all circumstances I can think of, on my GTP_login).
Despite being on ADSL 2, I don't really have a whole lotta bandwidth myself - the PS3 tends to show ~600Kbps up/~5Mpbs down, though it's more than that via measurementlabs NDT or speedtest. I did change my ISP connection style to what they call a "Gamer" connection, which lowers the downstream a bit, but bumps up the upstream and lowers latency.
It's been pretty solid since I moved to wired and did the DMZ, but UPnP worked sorta-ok-mostly. I still have to reset the modem occasionally (and I always do before a 3D3 race).
My first perception of online play was also ZOMG THE LAAAG. However, even with my being on wireless at the time, that was drastically skewed - once I raced in Australian rooms (with 4-5 bars), it was much better (albeit with DCs and the occasional black screen), so it could be more of a latency thing if you were connecting internationally.