Went to start car this morning for work. Turned the key and ....NOTHING. Tried again, after a second or two delay she fired up and off I went. Now the battery is about 12 months old and was 600+cca.
My question is do you reckon it was just a heat issue. It was around 43o here yesterday.

heat

nothing more mine did the same and I have a 460 CCA battery

I'd consider looking at heat in a different context.

If the car / engine / battery is cooled-down, pop your bonnet and feel the battery terminals, hopefully they will be fairly cool. THEN start the car (assuming it will start), then straight away feel the battery terminals again. If either battery terminal feels quite warm after starting the car, then I'd be thinking poor contact and resistence at the battery post, and needs a clean-up - by which I mean pulling that (or better, both) battery terminals off and using a cleaner tool to clean the contact surface of both the battery posts and the clamps on the leads (ie: inside the circle that clamps to battery post).

Your experience just sounds like hassles I used to have with a First Gen (TN) Magna - it had quite good plastic-coated battery clamps on the leads, but was a bugger for developing poor contact at the battery itself and being flsaky about starting. Could drive around on a shopping trip to a bigger town (I live rural), and it might be absolutely perfect 95% of the time, then fail completely at random. I suspected fusible links in the loom etc, but in every case either cleaning or just tightening the clamps on the battery made the difference.

Off top of head, can't think why higher ambient temp would give the issue you described!