Hughes500 - please do correct me if I'm wrong, but I believe it is an 18 month period to complete the theoretical exams, then a further 24 months to undertake the skills test. It certainly used to be, and CAP 804 states
(b) Pass standards
(1) A pass in an examination paper will be awarded to an applicant achieving at least 75% of the marks allocated to that paper. There is no penalty marking.
(2) Unless otherwise determined in this Part, an applicant has successfully completed the required theoretical knowledge examination for the appropriate pilot licence or rating when he/she has passed all the required examination papers within a period of 18 months counted from the end of the calendar month when the applicant first attempted an examination.
(3) If an applicant has failed to pass one of the examination papers within 4 attempts, or has failed to pass all papers within either 6 sittings or the period mentioned in paragraph (2), he/she shall re-take the complete set of examination papers.
Before re-taking the examinations, the applicant shall undertake further training at an ATO. The extent and scope of the training needed shall be determined by the training organisation, based on the needs of the applicant.
(c) Validity period
(1) The successful completion of the theoretical knowledge examinations will be valid:
(i) for the issue of a light aircraft pilot licence, a private pilot licence, a sailplane pilot licence or a balloon pilot licence, for a period of 24 months;
(ii) for the issue of a commercial pilot licence or instrument rating (IR), for a period of 36 months;
(iii) the periods in (i) and (ii) shall be counted from the day when the pilot successfully completes the theoretical knowledge examination, in accordance with (b)(2).
Source is CAP 804 Section 4, Part A, Page 3 (last paragraph) for anyone who's interested
Last edited by Aucky; 30th Dec 2012 at 23:51.