How difficult is it to apply for the visa de regrupacion?

Does anyone have a good website that can explain the visa de regrupacion better, a lot of the websites i have found contradict each other!

Also if my mexican husband is in the United Kingdom on a 2 year Spouses visa and he wants to get a work visa for Spain can he do all the paperwork in the Spanish EMbassy in London or does he have to return all the way to the Spanish Embassy in Mexico which would be a real inconvienince?


Thanks

Karen