This product Retails for £180 per roll of 50 metres. 
Here I am selling it for £4.78 per metre and you get exactly what you need without spending £180.

Dupont Tyvek Supro Roofing Membrane 1.5m x any length by the metre.

The best product on the market. Lots and lots of tests verify how good this is. Just Google it.

Buy the exact amount you need. Select how many metres x 1.5m by entering number in the quantity box above.
 Enter 2 and you will get 1.5 x 2 etc. 

DuPont Tyvek Supro is a durable, water resistant membrane that is reinforced with a laminated polypropylene nonwoven. This airtight, vapour-permeable membrane is extremely water-resistant, and can be used for all supported and unsupported pitched roofs.

Tyvek Supro does not need any soffit, tile or ridge ventilation, which can save time and money in the construction process. In addition to warm, hybrid and cold roofs, applications include Scottish sarking board systems, low-pitched metal roofs, and wall and floor applications.
Tyvek Supro water resistant membrane products are designed to withstand prolonged UV radiation and high temperatures, and come with full BBA and IAB approval for use in all pitched roof constructions.