It could very well be the hard drive. The boot loader has to be read from disk and loaded into memory. I have seen failing drives that were slow to spin up and initialize. The system has to wait until the drive responds.
Can you boot a Live session from CD or USB stick?
Thanks - I am sure you are right I wasn't sure on the boot loader. I was thinking of changing the hard drive as I have several spare. The one that is in there is older than the machine and that could well be the reason then.
I can boot a live session but it is on my spare/test machine so there is no data of importance on there - which is why I assume you mentioned it.
If I learnt anything in the early days of using linux it was that one needs a spare machine to check out a new release and updates before putting on one's main desktop.