OK, we've been in touch with the folks at moneysupermarket.com who provided us with much of that content, and they say:
"We contacted HMRC for confirmation and they told us that leasing cars and medical insurance can both, as part of salary-sacrifice arrangements, be used to reduce net-adjusted income (and therefore help you retain some or all of your entitlement to child benefit). Hope this helps."
From the research I have been able to do so far, it seems that only pension contributions can be deducted from gross salary to reduce net adjusted income if you're in the mid-range salary area and trying to reduce tax liability if opting to still receive child benefit. The info on the Mumsnet site says about cars and medical insurance which I don't think is correct - can anyone clarify please?