Which university will you be applying to? If you are applying through UCAS, you are REQUIRED to put down any certified grades. However I know someone who didn't put down his AS first sitting grade and got into UCL :p. (BUT I DON"T RECOMMEND IT!)
Even if he didn't report his AS grades in his first sitting, UCAS is able to obtain that information from the concerned boards. UCAS is like the big-bad who has control over universities and exams related to entry into university. The UCAS application form does not necessitate that you inform them of every qualification you took (in this case, the first results of AS-Level), it does not ask for information about resits. So there; he didn't 'fool' UCAS or UCL. In fact, by not mentioning maybe his 'bitter' grades he increased his chances of a conditional offer and once he met the conditions after a resit, he was accepted. Of course, this is what I've gathered from my knowledge and experience with regards to applications to UK universities.