drauk -
Think of the web based systems which, for example, transact billions of dollars worth of securities on a daily basis for the world's investment banks - do you think they'd do this if it couldn't be made reliable enough (for reasonable cost)?
Could you point me towards any info on such systems, as I wasn't aware any bank was dumb enough to entrust that sort of thing to a web server?
Financial systems aren't on the WWW as a rule, and if your bank's one is... change banks! They are closed systems kept well away from the wilds of the internet, and cost huge amounts of money.
NATS certainly aren't going to invest in anything similar for a mere NOTAMS site. Seems to me the only reason they won't bring back the old A8 etc. is that they would lose face in doing so - modern British businesses seem far more interested in face-saving than getting the job done.