John_Tullamarine
The circular referred to is AIC 151/1993(pink 91) 21 Oct 1993. If you try
www.ais.org.uk, it will guide you to subscribe. Of course, this circular was published before JAR's and so I recognise that amendments may have been made since its' publication.
The reference to the difference between this info. and FAR's in the accelerate-stop definitions is a mix of "Handling the big jets" and advice on take-off safety issued by the FAA in 2002, where I cannot find any mention of stopway distance used in the FAR calculations, but again I accept that this info. may be outdated, especially if JAR's and FAR's are being adjusted for similarity.
Whatever the calculation for obtaining V1, the crew should use this speed as a definite division between calling a stop or continuing with the take-off,
to do otherwise with the calculation, other than to use it properly, invites unwanted excitement.