Terms and conditions page says that they also trade as Bonus Breakaways, bonusbreakaways.com, Sun 4 U direct.com, Ski 4 U direct.com, Flywithusdirect.com, and Sun 4 U. These are trading names of Sun 4 U Limited.
They also trade as On the Case Travel whose contact details are
here telephone: 0800 091 4745
A search of
BT Directory Enquiries for
sun*
in
b2
returns one result:
Sun For Less Ltd
Tel: (0121) 631 3269
8-10 Navigation St, B2 4BS
It has a similar name and is also on Navigation Street with a similar post code. Not sure if it's the same company.