An interesting question Jan and I look forward to hearing more, with photos if possible!
On your dry and sandy soil, rather unusually for the UK I imagine that slugs are not an issue? In which case you could mulch larger plants with hay/straw/strulch. The latter has good writeups but I have not used it.
Because of this year’s drought I mulched celeriac 6 weeks ago with medium length cut grass, now hay, and have not watered them, so far so good. I would never do this for salads.
Mostly compost ticks the boxes, and yes when dry it takes a while to re-wet. Water a little until run-off, leave 15 seconds then rewater etc. Worth wetting thoroughly.
