The message
from Mike & Karen contains these words:

What is going to do most good for my garden - a couple of tonnes of
horse much every year, or this year should i try a couple of tonnes of
sharp sand in the hope it will make the soil less claggy and more sandy?
Or is there something else I could try to add?

I wouldn't rotovate heavy clay. As you've discovered, doing it in wet
winter weather does no good, and it can worsen the problem by leaving a
water-resistant clay pan below the depth of the rotovator blades, so
your plants end up with shallow root systems sitting in water..a bad
combination.

Adding as much humus material as possible is a good thing. Worms will
take it down into the soil, and their tiny tunnels also admit air and
help water drain. If you spread the horse muck in winter then cover the
patch with an old tarp or carpet or flattened cardboard packing cartons.
The worms will work quicker under the shelter, the rain will not leach
so much, and weeds won't germinate. Also, start compost heaps and
collect a s much free material as you can to fill them (sacks of leaves
lawn clippings and pet bedding from neighbours, bracken nettles and
rosebay willow from waste land, seaweed).

On the hard dry spaces between rows, where you're having difficulty
working a hoe, try spreading the cuttings from your lawn or any other
plant mulch you can get hold of. It smother weeds, stops a hard
soil-crust forming, and the worms will take it down to enrich the soil.
Bales of spoiled straw are usually very cheap.

A larger sharp grit would be a better additive than sand imho, because
clay is already composed of very fine particles. I would just scatter it
on top; plantings will gradually move it downward. If you have a quarry
or gravel pit nearby, it's worth asking what they have available that's
cheap.

Stack the lifted turf, green side away from light; it will make
valuable humus.

Janet.