Awesome. Mora it is!
Could a Groundsheet be used instead of a tarp? I assume the groundsheet is heavier, but i've found one that's 6ft x 8ft and it's £5.
You can use anything thats semi tough and water proof for a tarp. The benefits of tarp made for the job are pack size and weight, reinforced guy points and a big plus is noise reduction. Plastic more industrial tarps are very noisy in the wind.
Look at the DD 3x3 meter tarp which is pretty cheap and very good.