Rover 216 sli running problem?

Driving along fine 50 mph, suddenly no power as if electrics or fuel at fault, will idle, but missfiring, as soon as i press accelerator, engine dies, will start but not enough power to pull away again, towed home. spark is weak orange, intermitant,??? i could smell fuel from plug hole after turning engine to check spark with plug out, plugs were slightly black,dryish, honey colored underneath black oily fluff layer?? it has miss fired whilst driving 3 or 4 seconds,only twice, in about two weeks , i put it down to water condensation in fuel tank as fuel low for a few weeks, this was very sudden with no warning other than the misfire?? has always started and run fine whatever weather. although dash fuel gauge stopped working a couple days before breakdown.Honda Engine.