We built our house using NBT products, have ground source and PV, so I'm definitely getting in touch! I'm chasing them at the moment because I only just noticed (DUUHH) that for the past two years, since we moved in, we've been paying for sewerage when in fact we have a septic tank. That's over £600 which will make a much needed dent in the overdraft! If they ever get back to me, that is, it's been 2 weeks........