Are those over 25 denied access? If so you're probably breaching the letter (and certainly the spirit) of the Equality Act 2010 by directly discriminating on the basis of age!
They can do whatever they want - they just don't have to tell anyone what they are doing.
Run a small business? Don't want to employ women? Then don't!!
It is only when you tell someone that the problems comes.
Are you people thick or what? This is not some kind of recruitment drive its more of an open day for youngsters. I don't think they need worry about being prosecuted under the equality act 2010!