EK77WNCL
CPH, BRU, limited, very very limited, although connections are available. I may be wrong but I'd assume that BRU could, or should be quite good for African connections.
DUS utterly useless
I think that's a bit harsh, particularly on CPH - here you can connect to countless (well you could count them if you had the time / inclination) Scandinavian destinations few of which are served directly from any UK airport.
At DUS Germanwings does offer interline facilities, though I'm not sure if that's just on 4U services, and again good connections are also available at BRU to many European business centres - not so sure about Africa these days, SABENA used to serve ex Belgian colonial destinations but I haven't checked on what SN Brussels offer is.
If you're a small or medium sized regional (non London) airport then these hub links are vital, whether or not you have BA through LHR and if I were NCL management I'd be looking to attract LH to FRA or MUC operating at time that allow good connections to principal business centres. I wouldn't, frankly, be so bothered with the likes of ZRH and MAD at least to start with, and frankly, Istanbul would be way down the list of priorities.