From the Terms and Conditions on the Atlas Editions website
http://www.atlaseditions.co.uk/e/terms-and-conditions.html they are French owned and their actual (rather than PO Box) postcode is LE65 1JT.
From the Royal Mail website this postcode is unique to the following address:
M M Group
Unit 16
Coalfield Way
ASHBY-DE-LA-ZOUCH
LE65 1JT
the BT phonebook gives their geographical number as:
01530 562180
if you ring this number there is a recorded message "you have been contacted by Finnian International, if you wish....."
further probing and reference to the MM Group website
www.mmgroup.co.uk reveals that they are also called Teleperformance and are in fact a company operating call centres. Their contact details are given as:
Coalfield Way
Ashby Park
Ashby-De-La-Zouch
Leicestershire LE65 1JF
Tel: +44 (0) 1530 419 500
Fax: +44 (0) 1530 419 501
Suggest you ring the 01530 419 500 number in office hours (constantly engaged over the w/e) and please let us know how you got on.
PS
Following the merging of the Atlas Editions post with that for De Agostini without warning (which made me nearly loose what I wrote - Dave please note) it seems that these telemarketing organisations have many tentacles.