Despite the daunting grid and confusing preamble, the facile straight answers suggested this was going to be a pushover. Wrong. With lots of cold solving, jumbles, and putting entries in one or two letters at at time (what I call sticky label syndrome) this was a heck of a challenge and I was grateful for the easy straight clues. It did get a bit easier as the grid filled up, though I'm not sure I'd have completed this without the help of electronic anagram finders.
In the early stages I wondered why I waste my life like this, but as the solve progressed I realised I was enjoying myself enormously and was quite sorry when it was all over.
I believe eXtent is a partnership of eXternal and Serpent, both of whom have set Listeners in their own right.
Yes I think it's a numerical next week. Perhaps this fiendish challenge was intended to give those of us who don't bother with numericals something to do next weekend?