Just had a word with Zen and they told me it's "not something we provide to consumer customers, only business at the moment"
Just unplug the landline. It's basically the same service.
The E-Side copper to the exchange remains connected on SOGEA on every line.
The cost difference between a bundled service and SOGEA is more than often nil, sometimes pennies, and if you're lucky £1 or £2.
There's no difference to the xDSL performance.
With SOGEA the line rental is basically incorporated in to the price.
The only reason the price difference is so high in the example in the post above is because that's the price if you pay another ISP for the landline.