JAS stands for "Jumping and Style" and is run by BE. It is a competition comprised of showjumping and xc style knock down fences (indoors). There is a panel of judges who mark your round - ie. the speed of it/your style etc. and then your mark(lowest is best) is added to your jumping penalties from the sjing and xc section plus any time faults you incur and the lowest overall score wins
The top 10 go through to the final at Addington
and they run an intro, pre novice, novice and open class
www.bdwp.co.uk and look under "Holly Farr" - that gives you all the venues etc. or go to the British eventing website and look under events and then event series and click on the JAS stuff