Darn:
Have you looked at NotamPlot - it plots all the latest notams on a map just like you suggest and is excellent (may only work in the UK though?).
Actually, no I have not. But I have to say:
Why does it take a private individual to do what NATS should have been doing decades ago?
Why do none of the European handling agents we use have such a system? It does not sound like it will break the bank.
Why is such an obvious solution to the NOTAMS fiasco swathed in darkness and obscurity? Why does NATS not promote it? Embarrassed by their own inaction and inadequacy, perhaps?
If you have not seen it yourselves, here is NotamPlot. Downloadable free to private pilots - very generous of the designer:
NotamPlot.
.