I've asked Bikeregister to forward my details to the 'owner'. When they get in touch I'll request they provide crime ref no before arranging picking up of the bike.
It might also be worth asking for evidence that the bike, when stolen, had any of the components still on it now. A bike can change a lot in 4 years! They might change their mind about wanting it back if it's literally just the frame they'd be receiving.
I've asked Bikeregister to forward my details to the 'owner'. When they get in touch I'll request they provide crime ref no before arranging picking up of the bike.