Well for starters I can't use a heat mat at all as its a wooden viv, so I would need to change enclosure.
We don't have heat tape in the uk that I know of but it seems the same as a heat mat which does nothing for ambient temps, unless your talking about surface temps? If that was the case I could use a plastic tub with two heat mats statted one at 90 and other at say 80? Would that work ? But again I can't see it doing much for air temps in there, my house is around 68f this time of year....