Right folks I've been on to Eric, He uses a double pan or "bain marie" system, where you have a pan of water, with another pan or bowl sitting in the water in the first pan.
You heat the water and place the second pan in it, then putting your wax into the second pan to melt. Simmering the water, rather than actually boiling.
The wax can't get any hotter than the water, so you never go above 100 c stopping the wax catching fire and the leather being overcooked.
you immerse your leather into the melted wax and leave it until there are no more bubbles coming from the leather. This ensures complete and total penetration of the wax.
That's Eric's tried and trusted method.
He's been a bit off colour lately and not been getting much done, I'll have to get down to see him and take him out for a bit of fresh air, once I'm driving again!
cheers
Steve ( and Eric)