The key to bringing a go-kart project in under a £6 budget is using scrap. Not only should the wheels and wooden body be salvaged, but so should the nuts and bolts. Ask at a local junkyard or lumberyard, or check dumpsters if you have the owner's permission.
Pry apart the pallet with a claw hammer, making sure all the nails, screw and large splinters are removed. Sand off any rough sections. Use the planks from the pallet for constructing the kart.
Cut the wooden box in half, cutting width ways. Reinforce the bottom of one half of the wooden box with wooden planks. Cut two planks the same width as the half section of the box and lay them width ways along the bottom of the box on the inside. Push them flush up against the sides of the box and put screws down through the planks into the bottom of the box.
Cut a plank to about three quarters the length of your leg. Turn the box over and lay the plank down length ways along the centre of the underside of the box so that it sticks out past the cut edge of the box. Screw down through the plank, the floor of the box and into the planks on the inside.
Cut four squares of plank roughly a quarter of the size of the buggy wheels. Drill holes just large enough to fit the smaller bolts. Screw two blocks to the back corners of the cart, screwing from inside the cart, down through the wood into the block. Position them parallel and length ways with the kart, standing out at right angles from the bottom of the kart.
Screw another pair onto a plank half as wide again as the kart. Position this plank just under the far end of the long plank that sticks out from the centre of the kart, making a T shape. Drill a hole just large enough for the large bolt down through the both planks. Place a washer over the hole in the top plank, push the large bolt through the hole in both planks, slip a washer over the end and then tighten the nut over it.
Unbolt the wheels from the buggy axles. Place washers on the outside of the wooden blocks with the holes cut in them, place the wheel against the washer then put the bolt through the wheel and the hole in the block. Place a washer over the end of the bolt then tighten a nut over the end of the bolt.