The updated Plus version of Palm Pre and Palm Pixi are now available through O2 UK. Even though they are only minor upgrades, some of the stuff they bring to the table deserves attention.
With the Palm Pre Plus you get double the storage (16GB) and double the RAM (512MB). The design has been tweaked as well - the trackball has evolved to a trackpad and reportedly the keyboard has been redesigned. Plus now there's native compatibility with the Touchstone wireless charger (still sold separately).
With the Palm Pixi Plus you get the added bonus of Wi-Fi connectivity, which lacked in the original. That's pretty much all the upgrade it got, but it's enough.
The Palm Pre Plus goes from 99 GBP to free depending on the tariff you choose. Palm Pixi Plus is free on all Pay Monthly tariffs (with 18- and 24-month contracts, of course).