a-ha will do a signing session and an exclusive live performance in London on 6 October, to promote the UK release of 25.

Some info from a press release posted here:

“25 – The Very Best Of comes at the start of a bumper week for a-ha, as HMV have announced today that they will exclusively celebrate the album’s release with a signing at HMV’s Oxford Street flagship store at 6:00pm on Wednesday 6 October (due to limited time, 350 wristbands will be issued in-store only from 9:00am on 6 October on a first come first served basis).

This will be followed the very same day at 7:30pm by a very special live performance by
a-ha at the HMV venue Heaven. Tickets for this unique gig are exclusive to HMV customers who pre-order the album now. For a chance to obtain tickets go to HMV.com. Marking
a-ha’s 25-year anniversary, the first 25 people in the queue for a signing session wristband will also win a pair of tickets to the evening gig at Heaven.“