If you are interested in this promotional deal with Garuda Indonesia please look for limited travel dates till end of June and from 17th of August till end of March 2016. This is based on travel date of your outbound flight to Indonesia. Blackout period around Christmas holidays as usually.. To check your connection possibilities from your hometown we recommend to use Skyscanner tool. If you want to book your hotel in advance you may consider hotel booking agents such as Hotelopia. They are now also offering 6% promotional code for additional discount off hotel rooms. More details to be found here.
Booking samples
London - Biak and Sorong - London for £591
EN - London - Timor (Kupang) from £466
DE - London - Timor (Kupang) from €650
EN - London - New Guinea (Sorong) from £676
DE - London - New Guinea (Sorong) from €941
EN - London - Schouten Islands (Biak) from £488
DE - London - Schouten Islands (Biak) from €684
As a bonus Indonesia has recently put most of EU countries on their free-visa list. (applicable from April 2015).
Booking sample of cheap flights from London to Timor, Schouten Islands or New Guinea from £466 here. In this case you would be departing from London to Kupang on 30th of August and returning from Timor (Indonesian part) back to UK on 13th of September 2015.