What a great idea! I'm sure you'll enjoy it. If you move to an area with a lot of ex-pats from the UK, Spanish won't be quite as critical, but it really helps when you need to do things that aren't typical tourist activities. Then the level of Enlgish drops.

If possible, try to save enough that you don't absolutely have to work, or as least so you don't have to find a job that pays well.

I'm American, so I have no clue what an HNC qualification is, so I don't know what kind of work you are looking for.