If you haven't seen it already then this thread and the links to the Spanish moviledualsim.com website might be of interest to you.
I have elbuit's repack of gASK's 4.1.2 ROM (Acer V350 based) and it works fine.
Thanks for the link. I have tried this ROM and it didn't work for me. It might be my network provider - I need to add APN manually (OVIVO in the UK). I'll stick with 4.0.4 (rooted, with my own choice of launcher and keyboard) for now.