How can I descale my two-cup Gaggia coffee maker?

We've had it for a few years now but its been a slow death. First it stopped producing piping-hot coffee so that we'd have to reheat in microwave, then the coffee flow was reduced to a slow drip into the cup and finally, the flow stopped altogether. We live in hard-water Kent so can clearly see the effects on the tubes that draw water from the reservoir - this we can address - but the inner workings remain effected. Can anyone advise please?