birthing pool

hi i am planning a home birth with my 3 rd child. i would like to use a birthing pool but am slightly confused as to what type to use...has anyone used 1 they could reccomend? hire or buy? and are heaters a good idea? i hate the thought of the water  being to cool, so wanted 1 with a heater, but the only ones that come complete with a heater i have seen, seem to be to hire for alot of money...any advice would be much appriciated. xxx