1004 seems to have moved to Longstone recently.
1004 is the last of the ten buses to move away from Marine now that 391-400 have repositioned.
Overall, 496-510 (15) were replaced by 1002-1004, 670-680 (14) moving from Central and Marine. The April 6th service change may have changed the vehicle requirements which is why only 14 buses were added in place of 15.
As mentioned, 496 is currently in use at Marine, and could be required for the PVR increase on the 5 in September. This assumes that 751-758 will be based at Central to convert route 1 to deckers alongside 929-931. Alternatively it's just there temporary while Seafield and Thornton's are both busy with other refurbishments (and 751-758 may be positioned at Marine instead).
If 751-758 are positioned to Marine, then that should allow a few vehicles to move from Marine to Central for the 1. Alternatively 751-758 could also be split across both Central and Marine.
933-935 are currently extra at Longstone now that all of these movements have been completed, but I doubt that will stay the case from September. It opens further options for vehicle movements, as there isn't any double deck PVR changes at Longstone (feel free to correct), which means that any three buses from Longstone could be moved to Central to help with the conversion of route 1 as well.