I can finally share this now it's been gifted; blanket (and pattern) made by me.
Edited to add: thank you all for the lovely comments 💜
To answer a few questions; I'm not taking on commissions (because around work and life in general, this project took approx. 15 months) but I might put together a pattern at some point.
The blanket is 99% solid (4-round) granny squares, crocheted in DK yarn with a 4mm hook. At 18 x 19 squares, it covers a (UK) Double bed with overhang - see photo 2.
The squares were out together using the join-as-you-go method. Where a join is between two different colours, I used the yarn of the colour I was joining on to for the final loop of my stitches e.g.
Joining yellow to black would be as follows:
(UK treble st) work 3 rounds using yellow (Y).
On round 4, when you are working adjoining stitches (i.e. to join to black (B) square), work treble in Y as usual until you have final two loops remaining on hook.
Without breaking Y yarn, pick up / add in B yarn, YO and pull through final two loops to complete treble stitch.
Slip stitch into neighbouring stitch of B square (through both loops) to begin join, then without breaking B yarn, pick Y yarn back up to work your next stitch.
Jumimo was a typo; it's been a long day!