Hi Lisa, we have a newhome stove in our van, three plates LPG & the fourth electric.
Had the same slow heating problem with ours & the gas company said first check the regulator which they did for me but it was OK. So we took the jet out of the large plate (front RH side) & fitted it to the medium burner (rear RH side) I then had the gas Company slightly enlarge the orrifice of the jet taken from the medium plate & fitted it to the large plate.
It made a world of difference as we can now control the heat rather than wait an eternity for the billy to boil.
Take care if you do something similar, the flame should burn a healthy blue, not orange or white
barry, May 2011