I too would like to know how to get back to RUU in the UK.
I've an unbranded phone bought out right and getting fed up of not being able to use banking apps.
I've used RootCloak and it's working for Halifax (although at present Halifax is just mobile web rather than an app) but not for Barclay's and Lloyd's.
Anyway, Googling how to unroot phone I found a link to this:
If anyone is willing to pay for it, looks like we might be able to get an RUU.
Then there's a couple of Persian sites when I Google'd the ROM:
I've translated it and tried to join up but it couldn't get past the sign in screen, lord knows why.
So there we are, possible options to return to RUU. If anyone knows how to get around the banking problem i'll stick with root.