There is a page here:
http://www.aswltd.com/adultmet.htmIt's an American page so the books may not be readily available in the UK, but it talks through various adult-suited methods, i.e. ones where you aren't playing Twinkle Twinkle Little Star.
I have the Orr books (vols 1 & 2 in both soprano and alto). They start of very basic, with G for descant or C on the treble. It doesn't waste time teaching you about notes on the stave, it just tells you the note name, how to finger it, and then gives you some exercises on it. It only mentions note values with respect to tounging, if I remember rightly - i.e. how to sort your toungue out for demisemiquavers! There are some "real tunes" in the books, but they are often German and things I've never heard of, at least until towards the later bit of volume 2

Volume one of each covers the lower octave + 1 note, i.e. on the descant from C up to D. These notes all use the thumb-hole closed or for the top note, totally open. The half-open/cracked/pinched/whatever term you prefer isn't introduced until the second book. The second book goes all the way up to the highest notes.
I haven't looked at any other adult method books so I can't comment.
Having said that, the Orr I ended up getting via eBay and AbeBooks. One thing to note if you do look for these books secondhand is that the covers for descant and treble are identical. The words "soprano alto" appear on every book, with the instrument that book is for underlined. So it'll say:
Hugh Orr Basic Recorder Technique Volume 1 Soprano
Altoand that'll be the volume one for treble. If you see the book advertised secondhand, people selling may not know what it is they are selling, so they sell it as for "soprano alto"; they also may not state volume one or two. I ended up emailing a lot of people to end up with the set of four (after which, I decided I probably didn't need the volume 1s

)