Working out what else I will need.

The stained glass window under construction needs more lead and glass. I have been trying to work out how much of everything I will need. It is impossible basically but postage is only £8.50 so I can order more if necessary. I was under the impression that postage was £25 which would have made me reluctant to re-order. I cannot do any more till I get some steel reinforcing bar.
The size of it is over 6 feet long (1.8m) and 2 feet wide. I have done similar sizes in the past, they end up really heavy, hence the need for the bar.