From Terms & Conditions on booking with GSM:
Changes to Flight Schedules
We reserve the right to amend, introduce stops, cancel or consolidate flights as necessary to achieve the high load factors required to maintain profitability whilst offering low fares. Whilst we will try to avoid making changes, we will of course notify you of any material change where it is practical to do so. In this instance we will contact you via your registered email address if the booking was made on the website. Only if the booking was made through our reservation office will you be notified by post. Therefore it is important to inform us of any changes to these details. Changes made at the last minute for industrial action; operational reasons etc; will only be posted on our website. For these reasons and because it is prudent to do so, you should utilise the reconfirmation link on our website prior to your departure, which allows you to view your booking 'live' in our system......