Here are a few links to competition organisers and calendars and information that are worth keeping an eye on.
Royal Stennick Challenge. A Kent Competition held two or three times a year.
Academy Cup series (U14, U12, U10). A series of four individual and team events with cash prizes!
EF London Region. A selection of Senior, Intermediate and Junior Competitions. Their flagship event is the London Youth Championships, qualifiers for the British Youth Championships. Also see this site for training opportunities
If you are 17 or under and have been fencing at least 6 months and had a go at a County or local competition then you may want to consider taking part in the Leon Paul Junior Series (LPJS).These are organised by local clubs, sponsored by Leon Paul with points being accumulated at each competition to build a score and a UK ranking with a prize at the end! But even if you don’t go for points most of UK’s successful fencers have competed in the LPJS.