is it ok to cover the soil at the base of the plant to create more light or will this effect the plant in a bad way e,g the leaves start reaching downwards towards the foil, please help
Tinfoil is always not good to use. However, for hydro growers, some white poly or mylar is just fine, just make sure that its not going to restrict your stalk as they do get fairly large, anywhere from 1-3 inches in diameter. However, having the light reach your soil is benifical as it heats the soil and keeps damping type disease down to a minimum, so while it works for hydro I'd not recommend it for soil.
If you are worried about the bottom of your plants not getting enough light, you could always just drop $20 on some flouros and add a little side lighting to your grow.
Yeah I heard about people putting down mylar, but didn't know what they were growing in. I've got two 20w fluoro and one 8w. It's not much, but they're just sprouts right now and I am going to see if I can get into town to pick up 6 CFL's in a couple days and some better tubes for the fluoros.