Jetset.
LGW standbys cover both long and short haul as you state. At LHR short haul operate airport standbys, and long haul operate a mixture of QRS and 2hr standbys.
QRS is an acronym for Quick Response Standby. You are based in either the Arora or Sofitel at LHR and you are on 45mins notice. QRS lasts for 3 days and is in 8hr blocks. Often the call out is to go direct to an aircraft.
The majority of stand by is via 2hr standby. For this no accomodation is provided and a minimum of 2hrs notice is given. Again 2hrs lasts for 3 days in 8hr blocks. Both standbys are part of a 9 day standby block duty with the remaining time being taken up with 24hr standby.
The general rule is that QRS is only used for issues at or near report time. Any other issues resulting in crew shortage are covered by 2hrs. Ie if an individual reports sick in the am for a pm flight, a 2hr standby will be notified.
I understand that at LGW airport standbys must be used for long haul within the first 2hrs of the start of standby to protect duty hours.
That would work for our shorter long hauls but not the longer range trips as scheme states 'if a crew member is on stand by duty on immediate readiness at an airport , then the allowable FDP is calculated using the start time of the stand by duty.'