I don’t think there will be a schedule for helio flights. They have routes around and across London according to if they are single or multi engined types. Alan Mann Helicopters being based at Fairoaks will if going anywhere North head towards LHR. They are usually guided to the approach end of the landing runway and then cross between airliners. The clearence is called ‘special VFR’
If you have a airband radio it will be on 119.9 or 132.7.
mmitch.