Meister Emson roofing contractor provides all your needs in lead roofing:

Lead is still invaluable as weather protection for many traditional British buildings. Even when not used as a roof covering, it can be present as a gutter or a flashing, or a bridge at awkward junctions between walls and roofs.

Lead sheets come in different weights and given code numbers. Code 4 and 5 for example is used for flashing. The number indicates the lead thickness to weight ratio in lb per square foot.