As for the overnight stay, will Stansted let you stay in the airport open lounges.
Last Flight to Stansted from Dublin arrives at 22.50 by the time you de-plane and collect your bags it will be nearly midnight.
First flight to Jerez is 07.00, check in is probably 06.00
A few drinks (even coffee !) and forty winks on the chair, a bit of a freshen-up in the toilets and it will be time for check-in.
Thought of this type of thing when thinking of travelling to the Ireland away games. I have not tried it myself....