What thickness wire should I use from the battery to the starter motor and from the battery to the engine then chassis? I looked at getting pre made jobbes from Vech Wiring Products but the pre-mades seem to top out at 19mm squared. I would like to make my own but fearful of doing a bad crimping job. Is this crimping easy and with what tool?

Oh the Positive cable to the starter will be about 500mm to 600mm and the earth about 450mm - 500mm?

Umm! It all depends. Assuming you are using a standard starter with a standard motor 16mm would be OK but 25mm would be marginally better if the battery had a higher international resistance (loosly approximating to capacity).
Crimping is dead east however. Get tinned lugs from tool station for example - they will come in 10 16 and 25 mm sizes. Get a bit of angle iron and put it corner down in a vice jaws Put the lug on the cable and rest it in the angle iron and then whallop it with a pin punch - around 8to10mm once only with a club hammer.
Perfect every time once you have the knack.

Hmm this is a case where a pic is worth a k words I think!

Back to the cable size. As an example I have a high compression v8 with a motorcycle battery to start it. Using 25mm cable with a geared starter motor works perfectly. If I used a car battery possibly I could get away with 16mm. If the standard starter was used I'd need 25mm plus the car battery.

Cheers!

Btw you earth lead seems rather long

I was probably being a little over zealous with the length of the earth lead. I think I will go for the 'make your own route'. Does anyone have any pics of this process?

Thanks for the advice!!

no one got anything else to say?

My starter motor cable is Bl**dy thick and about 2m long. Soldered fittings on the ends using my brazing torch.

Starts first time .

Paul