Alva gas heaters not up to scratch

We have bought 2 Alva gas heaters from Builders Warehouse (BW) and have had no end of problems. Once the rubber seal of one of the heaters came off, which was fixed, and then later both gas heaters started leaking gas. When we returned both heaters we were informed that proof of purchase was required for BW to send it back to Alva. Whilst we have the dates of the purchases, which has been fine on previous occasions, BW claimed they could not find the details on the system, and therefore neither them or Alva can assist us.<br> <br> We have asked to speak to the manager on over 3 occasions and never even been able to speak to him or get him to return our calls. Very frustrating all around and our 2 gas heaters remain at BW....