Compton3Bravo, it appears that GLM is a start-up. This extract is taken from the Routes Online website:
GLM Airlines
Netherlands-based GLM Airlines is seeking to serve European markets.
GLM's focus is to achieve high-efficiency operations and competitive ticket prices, even with smaller aircraft and without losing profitability.
The carrier has achieved this by introducing a fully integrated web based ICT-system (IOS Meredon) - a solid solution designed to minimise overhead costs and named ‘LOCC airliner' (Low Overhead Cost Carrier).
And according to Groningen Airports Route Shop Profile, one of their wishes is for a London Route, while proving a smaller demand for Norwich as well.This could be an interim route, or trying to get the cheapest way to serve both.
Looks like there could be an element of truth beehind the rumour
RC