Good Post, lots of valuable info.
Some more food for thought.
Being told by Solent (who, relatively speaking, were not busy)
Judging how busy an ATC unit is based solely on the frequency you are using can't be relied upon. The ATCO concerned may have a whole host of other frequencies and tasks going on, that you will not always be aware of.
Those nice people at London Information (124.6 / 124.75) might have been able to help, but granted, they do get very busy frequency wise.
There's also D&D, on 121.5. They're not just there for emergencies. Indeed, given that they would untimately been invovled if Shoreham had started overdue action on Gengis, they'd probably appreciate the call to let Shoreham know.
(Easy on the ground isn't it? Not sure I'd have been able to think it through in the air)
Rgds BEX