The last time I competed (was 100% conversant with the BAeA rules) there was no requirement to hold a licence!
A non-licence holder could compete with a safety pilot but would be deemed "hors de combat". I frequently competed against Harry, a delightful octagenarian who fell into this category!
To fly solo at a comp one does need to demonstrate proficiency to a suitably appointed person prior to the comp and not within 5 miles of the comp venue!