heat mat heating wiring

Hi i have got exo terra terrarium 24"18"18" for my leopard gecko it only takes 35w bulbs so got one bulb and a heat mat on one side but can only get to about 83f temperature :( my stat is just above substrate anyone had this problem ?

I have a snake with Heat mat and was wondering can I change to a UV lamp, because with new snakes, I am sick and tired of spending £30 for themostat and £15 for the heat mat. I think it would be cheaper and easier for UV bulb and wiring, you thoughts please.

I'm planning to use a heat mat for my leopard gecko but I have a complete glass tank and no holes through which to put the wire through. Should I drill a hole just big enough for the wire or is there a better way? Also which is better for heating, heat mat or lights? Oh and I'm going to make a...