Or, if you have an IR, take an airways route.
Since the flight planned route will never actually be flown, en route notams are hardly important, and the notams for the "end bits" can be obtained from any other briefing site, UK or foreign.
If there was another free site that does a narrow route briefing, I wouldn't give ais.org.uk a second glance.
Is there another one, or perhaps even a pay site?