I did the NEBOSH National General cert about 3 years ago now - did most of it by distance learning (sending assignments into a college-based tutor) then went to the college for 2 days to do the exam.
I was already working in the H&S department of our company (did my IOSH MS a couple of years before) and it was definitely a good course to do.
I found distance learning to be a really good way to study - my boss has recently completed the NEBOSH Construction Certificate and found the content to be 99% similar to the General Cert.