[New shoot]

I'm on clay as well which doesn't help with that.

Me too and I find covering with plastic leaves a green covered, totally sodden soil to dig into in spring.  I'm not far away from Sunny as the crow flies and while we both have heavy soil, her plot drains way better than mine.

If your soil is light BumbleJo, you should be fine to cover, but plastic or cardboard will attract slugs.  They sit wet on the soil surface, whereas membrane dries out.

[JayG]

If your soil is free-draining the winter rains are unlikely to leave it waterlogged in spring even if you don't cover it, although being free-draining most of the nutrients in the upper region of the soil will be leached downwards and therefore out of reach of your spring planting.
Having said that, sandy soils like mine are not naturally fertile anyway, and will therefore always need more feeding than most other types.

Apart from encouraging slugs, covering with black plastic seems a very unnatural thing to do to a complex ecosystem like soil - I only cover my soil when I have something growing in it I'm trying to kill (like a previously rampant Fargesia, for example ), and even then I use weed control fabric to give the soil at least some chance to breath.

I reckon there's a lot to be said for green manure, but not if you're a lazy type like me! 

[Aled]

Put the first cover of cardboard down today.
Cheers
Aled

[Mr Rotavator]

I cover with seaweed after the first winter storms then dig in during the spring.

[Flowertot]

After years of not covering, last winter I covered some beds with a thick layer of composted manure and others (for root veg mainly) with plain compost then weed matting (not plastic) held down with plastic pegs and a few bricks for good measure. It was so successful I’m in the midst of doing it again this year.  The reasons were Sunny’s 1, 2 and 4 reasons above plus my third reason of keeping the weeds down until I want to sow seeds/plant out. It made my life SO much easier in Spring and enriched the soil/helped its structure.  It also had the added benefit of weakening the perennial weeds (horsetail and bindweed) as light was excluded for some time.