All are same....
ZTE Blade - Original phone from ZTE
San Francisco - Orange rebranded ZTE Blade
Dell XCD35 - Dell rebranded ZTE Blade
What we all have is the Orange rebranded ZTE Blade called as San Francisco. So just forget about ZTE blade and assume
ZTE blade = San Francisco in specs.
The phone when introduced by orange came in OLED screen but later on only TFT models were available. So if you are going to buy a brand new, most likely it may be TFT. 3-4 months old used ones may be OLED but no way to know until you have phone in hand.
I know gsmarena lists some physical difference between zte and dell but ignore them. They are same.
Moreover the dell one is with indian warranty but with double price to what we got and it has less (256 mb) RAM vis-a-vis the ZTE which has 512 MB. But there is a mod to make dell to 512 MB but that will void its warranty. Dell is only TFT screen and OLED is considered to be better than TFT.
But dont buy ZTE from UK site assuming you will get OLED. 99% chances are you will get TFT.
In short you should be looking to buy the ZTE Blade / San Fransisco from UK website like ebay UK.
If still unclear, you can call me and i will explain. (PM me if you want my num
)