I've just purchased an Orange San Francisco and was looking for a case/screen protector.
I then read a lot of posts about how the Samsung i900 screen protector fits perfectly, and I'm a big fan of Zagg's products after using them on two iPhones.
I then found that the Zagg full body protector for the i900 is 75% off, as shown in the picture the screen protector is separate from the rest so can be used in isolation.
It's still a good deal for the i900, if using for an Orange SF you could cut up the the back and have a spare or use it on another phone.
The product itself is $6.25, shipping to mainland UK is $5.30. I used Quidco to get another 20% off, I noticed there are some codes around but didn't use any. Lifetime warranty on this too and shipping is pretty quick.
Links to pics of the screen protector from a i900 on a SF: http://www.avforums.com/forums/mobile-phones-pdas/1332197-orange-san-francisco-zte-blade-android-2-1-wvga-oled-capacitive-fm-satnav-109-a-3.html