Uk to Spain

Hi
We are looking at bringing our uk to Spain and eventually changing to Spanish plates. Couple of questions if you can help.
When it states in a twelve month period what does that actually mean Jan to Dec or 12 mth from end of the 6th period.
What is required to transfer to Spanish plates.
Any really good companies that can be recommended to do all the paperwork and transfer.
How long does it take and approx costs.
Thank you in advance

ALL those questions can be answered by Leigh Blann at www.spanish-number-plates.com

Good solid advice from someone who knows their business. Highly recommend.

Thank you

It's 6 months in any 12 so not related to the calendar.