I emailed PreSonus yesterday, asking about the crossgrade.
In my inbox this morning I got a message from PreSonus support telling me to access my account at their site and there was an answer waiting for me there.
Once at the checkout, and I had added a coupon, as directed, the price came down to $168.27 (converted to £130.59). The Black Friday deal at PreSonus was £172.20, so I call that a result, and I took them up on their offer.
That said, it was probably a bit reckless of me and I now have fully paid up versions of SONAR Platinum, Reaper and Studio One 3.
I fully intend to stay with SONAR so Reaper and Studio One 3 are my insurance policies, if you like. I have been enjoying my time, over the weekend, getting to grips with SO3...
Cheers, and thanks to PreSonus,
andy