Sounds quite plausible but I don't remember the usage from 'back in the day'.I'm not certain about this but I think it goes back to the days go Norwich having three stations. Norwich Victoria - the original terminus of the Eastern Union Railway - would have been the "High Level".
also makes you think of other 'local' names in the area:
Jubilee sidings at Norwich.
The 'Arcade' at Ipswich (PLatform 1)
Foundout, also known as the Table Rod: Fuel Road
Field Sidings on the Up side at Ipswich.
Jubilee sidings are still known to many as 'The Back Road'.