Just a note of caution: the above posts suggest 'planning' OCK-ASCOT-BUR-HEN and 'listening out' on 119.9. Just be aware that you will need a CLEARANCE to enter the LL CTR!! Consider also that you are only 800 ft AGL, so it's a good idea to keep spotting fields which would make likely landing sites should it all go quiet.
An alternative route would be BIG- Isle of Dogs - Lea Valley- BPK with the permission of Thames Radar (132.7) and this has the benefit of usually being 'not above 2400ft' with the better glide clear options that this allows.