I looked into getting bumhuggers but when I asked on CNT the general opinion was they are not that great for very heavy wetters. They basically said they are good, but not as good as say Upsey daisy night nappies or WNNN.
Natty - have you thought about using wool wraps for your little one? They allow some of the moisture to evaporate so they don't stay soaked all night? I have just bought some and the plan is to eventually use it at night with an upsey daisy nappy or a WNNN. You only have to wash them every week or 2 and then soak them in lanolin to keep them waterproof. Really easy though. I have just done it for the first time and when it is dry we are going to try it out in the daytime first of all as I don't have my night nappies sorted yet and for night time use you should lanolise them a few times first. BUT it should really help the heavy wetting situation.
I have just ordered my custom upsey daisy night nappy! YAY! Cost me £15 but if it does the trick it will be well worth it.