At the end of winter about February or early March you could cover a small section of your plot with cloches or plastic sheeting (black is ideal but clear is also fine). This will have the effect of helping to warm the soil up and dry it a little. It may give you a bit of a head start and mean you could sow a bit earlier, say the end of March. It is worth keeping on the cloches and plastic (if you used clear plastic) after sowing to encourage germination. Once the seedlings are through you could raise up the plastic above the crop using supports . You could then swop over to fleece or some fine crop protection mesh when the seedlings are a little bigger. These will allow rain to penetrate. Early sowings of parsnip, carrot, lettuce and radish will benefit from soil warming. In terms of quick crops such as radish and lettuce it may mean you get a crop to harvest a week or two earlier.
