I love your commitment! and echo all you say. Mulching with layers of straw is best in hot, dry climates and does indeed breed endless slugs in most of Britain, much of the time. Also where there are already many weeds, there is a reservoir of existing slugs so the first year is always harder from that point of view, until one achieves bare soil.
Poolfield, I hope you have no weeds at least on your beds? And your surface layers of mulch are slowly rotting and being taken in by worms? I think I would remove all unrotted mulch to a compost heap, and any slugs you find. Your problem is paths…..
Wyrdwitch, your couch sounds well established and won’t succumb to half a year’s mulching, I suspect it needs a whole season. Even if you mulch the paths, it will keep popping into your beds. (And vice versa for Poolfield, you needed to mulch paths too). I would be tempted to cover the whole plot with membrane, expensive though it is, plant through it next season, remove any weeds that pop through planting holes, maintain slug traps or whatever….. Also if you had any spare compost to spread before laying a membrane, growth will be stronger.
Then in the following year you could remove the membrane and grow in clean soil with many less slugs.