In reply to Tom Slater:
Youth A is the most competitive category for the GB bouldering and GB lead team with several very good climbers. The YCS is a fun competition and good for getting competition experience but will not get you on the GB team especially not in Youth A. GB climbers are ineligible for the YCS.
Look for some of the Boulder comps at walls in the Autumn. If you are Lakes based then the Depot Youth Cup at Manchester Depot and Rockfest at Rockover, Manchester might be good to get you going.
To test yourself against the lead climbers , come along to the BLCCs in September in Sheffield. This is one of the events that counts towards selection for the Lead team.
Then keep an eye on the BMC website for information on the new GB development squad. The try out weekend should be at the first weekend of December.
In the new year, you will be able to enter the YCS and there should be news regarding the first Open Youth events of the year. The Open Youth comps are absolutely key to gaining and retaining GB places.
For additional Boulder practice on world class setting, look out for the CWIF competition in Sheffield at the Climbing Works usually in March time. If you are prepared to travel further afield, then enter some rounds of Blockfest (London and South East based). Then next July, there will be the British Bouldering Championships.
The best way not to miss any comps or events is to follow the BMC on Twitter together with a range of climbing walls.
With regards to training, the grade range for YCS is on the BMC website but most areas will push the grades harder. The key thing is to get experience on a range of walls with a variety of different route setters. Push yourself to practise using holds and moves that are out of your comfort zone on lots of different angles. You mention a moonboard on another post and while that will make you stronger and impact on your climbing long term, short term you need to work on training on the sort of walls and climbs you will experience in competition.
Good luck in all your climbing endeavours. Keep enjoying it whatever else you do.