Hi Asif. Yes bring the seed trays to warmth, until you see shoots of growth. Germination and subsequent growth will be much stronger.
The fruit trees, I would prune about a third to half of new growth now, then another third to half of the new season growth in July. How much you cut off depends partly how big you want the trees.
If you grow perennial veg or clover between those trees, the tree vigour will be compromised. I would grow onions or garlic. They finish in summer when trees often runs short of moisture.
And you are right, clover might increase slugs.
