You probably need to replace the clutch slave cylinder on top of the gearbox, then re-bleed the clutch.
It sounds like it's had a seal failure, as the handbrake light came on (this light also signifies a low brake/clutch fluid level).
Your brakes are fine because they have their own circuit.. they just share the fluid reservoir with the clutch.
If you pick up the pedal and release the slave cylinder by hand (assuming it's not leaking fluid all over the place) it may recover enough to allow you to move the car.. but if it's leaking, it may not make it, so don't drive the car otherwise). Slave cylinders are aboot £30 and easy to DIY fit.
If it's not visibly leaking, then the clutch thrust bearing may have collapsed
(or worn its way through the clutch plate prongs) which would have caused the fluid level to drop since the plate is about 3cm further forward than it should be.
If your clutch was making a grating noise for a while, before it failed.. or was heavy... and there's no fluid leak on top of the gearbox, then that's what it is.
It will require a clutch change job ("just" £80 on the 'bay.. but "plus labour" which will hurt a bit).
If you change the clutch and you can't remember the last time it had a new slave cylinder, stick a new one of those on at the same time.