What end does 1342 astra start?

I assume by 1342 you mean the firing order of the cylinders. By convention, cylinder number one is always at the crankshaft pulley end of the engine, so on the Astra, if you are stood with the bonnet open looking at the engine, cylinder 1 is on your left. Admittedly it does get a bit more complicated with "V" engines, but that does not apply to the Astra.