OK, looks like it wasn't my hard drive that was the problem...
Yesterday, after hours of use installing on a new HD (hours due to net install), I booted up and it worked OK.
I then rebooted at one point and LILO gave me:- ERR=2 Unrecognised compression format. Halting.
Another reboot booted the kernel, but it had millions of Drive Seek Ready errors and DMA errors, then halted at INIT. I checked the cables (in fact put new ones in), and noticed that the hard drive was SUPER-hot).
Leaving it for 30 mins, it booted OK. Does anyone think it may be overheating? Or poss a RAM error? (So the kernel doesn't load up properly).
Any ideas?