Is it possible that I was hearing signals from the US? I had thought of 160 as being sort of local band.
It's certainly possible. Contest stations have exceptionally strong signals and conditions were quite good last night between England and here in Maryland. I've worked to have good 160m reception from my location but these stations were loud enough that I could probably have heard them on just a wire.
There is DX potential on 160m. I've worked 131 countries there, and sometimes Europe comes in strong. Here's a clip of Geoff, G3XGC sending his name and signal report to a stateside station: http://n3ox.net/files/g3xgc_101307.mp3
I think one of the reasons it seems like a "local" band is because the DX is so much weaker than the locals 90% of the time and the locals are so strong. It's not like 20m where you might have the same signal strength from mainland Europe and from the Midwest USA. The DX is often near the noise level, while the locals with even modest dipoles will have bone-crushing signals because local propagation is so good. So you might not even try to listen for the signals at the noise level. And the DX is almost all on CW anyway. Every once and a while you'll find some SSB DX activity in the 1840-1850 frequency range but it's rare.
If you know to look for it, though, the DX is there. My best DX distance-wise is Australia. The bulk of my DX contacts have been with Europe, Carribean, and Central America. I made a map of my 160m QSOs, most made over the past four years:http://n3ox.net/files/N3OX_160QSO_013011.jpg
Most of the USA QSOs shown are from contests.