Thanks,
In the end I've decided to go for the Opus. I just don't think I need the ability to annotate, and I'm happy to surf on my phone rather than on my e-reader so while Wi-Fi might be cool, I felt I couldn't justify the extra cost of the Orizon.
Finally, after a bit of price research, I found that Tesco Direct have the Opus for £130 with free delivery, so that settled it in the end.
It should arrive tomorrow
John