I received an answer and apology from UDiscover regarding box set:
Thay still say its limited until stock, but not what that stock might be in numbers. Who knows... I am also going for deluxe cd.
Dear Peter,
We wanted to inform you that initially this was advertised as a uDiscover exclusive limited to 300 units only. This was in fact only a UK exclusive for uDiscover and so some of you may have seen the box set available from other online outlets outside of the UK. Also, due to unprecedented demand, we have been informed that the initial planned run has been increased in quantity to allow more fans to get hold of a set. It still remains limited and only available while stocks last.
We would like take this opportunity to sincerely apologise for this miscommunication and any inconvenience this may have caused you. Should you now wish to cancel your order, please let us know by replying to this email and quoting your order number.