did ALL the electrics die, including the stereo ???
did it stay dead for 5-10 minutes then come back to life...?
if so its a problem with the starter motor and solinoid.
quick fix is to pop the bonnet and tap the battery on the bit between the terminals (theres a big overload bi-metalic strip in that part of the battery, if you gently tap it with a hammer it will be encouraged to pop back into place).
(it worked for me, as a quick fix, and diagnosis)
i had similar problems and ended up having to replace the battery and starter motor on my laggy1 (twice over 2006/7)
the current overload by the starter caused the battery to eventually fail. i replaced mine with the biggest i could get that would fit, have now got a 130A battery, it was originally a dinky 65Ah one.