Yes each UC passenger is allowed to take one guest in to the CH with them.

VS guard access tightly and so appealing to their 'good nature' won't help. They have heard all the stories before re special anniversaries, reasons for the trip etc etc and it won't work.

It has been possible in the past to purchase on the day entry for £60 but this depends on how busy the CH is going to be that day so there are no guarantees this will happen on any particular date and are not sold in advance.