Sorry, but I don't agree.
The level in Spanish Bachillerato is more or less the same as A-levels in England, at least in theory, although in practice there must be differences, the same as it seems there are in the GCSE exams you are preparing for. I have never seen one of those exams, so I don't know if they are more difficult than the Spanish ESO ones (probably so).
Both in England and in Spain you have to study for two more years after compulsory secondary education (ESO or GCSE) before you can study at a university. The difference is that in England you have to get a certain number of A's, B's and C's on a certain number of subjects if you want to study at a specific university, whereas in Spain each university establishes a minimum grade at the "selectividad" exam ("university access exam" would be the literal translation of its official name, "prueba de acceso a la universidad").
