You can start the works if the Town Council does not notify you any required information before 2 month since the date of your application. That is called a lincese or permit granted by positive silence, which, actually, is an express administrative act, that can not be removed by an ulterior decision of the town hall, except by a very specific and difficult administrative proceeding.
After the term of two month (plus, if applicable, that of the extension as consequence of suspension of the term for deciding when the Town Council request for repair of rectifiable errors), without being notified the applicant of the decision, there is applicable the legal presumpion of positive administrative silence. This concept arises when a public administrative body fails to reply within the stipulated time limit to a complaint lodged against its procedure or a challenge to its decision; it is frequently used as the basis of an appeal through the judicial review procedure of the administration acts; in modern spanish administrative law, silence means, generally, consent, in the sense that the law stablishes the presumption that administrative silence is decisive in favor of the applicant. http://www.iurisconsulting.net