From their site (Edited)
      
Simply Malaysia is a trading name of The Freedom Travel Group Limited
Registered Office Hamil Road, Burslem, Stoke On Trent, ST6 1AJ.

Simply Malaysia a product of Welcome Abroad Travel is a trading name of The Freedom Travel Group Limited.
Registered Office: Hamil Road, Burslem, Stoke on Trent ST6 1AJ.

Freedom Travel Group Limited is a subsidiary of United Co Operatives Limited.

So here goes.

http://www.travel-travel.co.uk/
Travel-Travel.co.uk is a trading name of The Freedom Travel Group Limited.  0800 983 6542

http://www.freedomtravelgroup.co.uk/contactus.asp
Freedom Travel Group   0800 050 1022

http://www.online-travel.co.uk/
online-travel.co.uk is a trading name of the Freedom Travel Group Ltd    0800 983 6541

http://www.cooptravelshop.co.uk/visitabranch.asp
This gives all the branches operating under the coop name, complete with landlines

Other than the 0800s given, the main offices have hidden themselves behind the 0870

Hope some of this helps

I guess this is them (same 0870 number):

In Travelller (Leicester)
Address:      265 Hinckley Road      
     Leicester
     LE3 0TH
     Leicestershire      
Main Telephone:      0870-112 1170


So from 118118.com:

     Intraveller.Com      
     265Hinckley Rd, LEICESTER, LE3 0TH            
0116 247 3100      

Please try this and enter it into the main database (as both Intraveller and Simply Malaysia) if it is correct.