I took the CELTA with Cambridge School in Granollers (a 40 min train journey from Barcelona Sants). For further info see http://www.cambridgeschool.com/
and click on 'Teacher training CELTA/DELTA on the far right.
The CELTA is THE most intensive thing I have ever done, and mine was a five week course! I have no idea how people survive the four week one. It was worth it though, as I came out with a Pass A.
So, what can I say about the course? Firstly, despite the pressure, I really enjoyed it. The tutors were approachable and supportive, as were the other teachers in the school, many of whom had taken the CELTA there themselves. The input sessions were, for the most part, interesting, and the feedback from teaching practice was developmental rather than judgemental.
Please let me know if I can be of any further assistance.