Simply cloches and vegetable garden irrigation
When starting a vegetable garden in the spring one of the first crops to be sown is often peas as they germinate at low temperatures and grow in low temperatures. In February creating a small cloche using some wire and plastic secured between two wooden pegs held down with the string threaded along the cloche through loops created in the wire.
https://www.toolstation.com/galvanised-garden-wire/p38339
https://www.toolstation.com/carpet-protection/p57058
You can also use the plastic sheeting to plant early season potatoes using the sheeting to add some frost protection in the first 6 to 8 weeks from February onwards. Then later the plastic sheeting can be removed and the potatoes earthed up
Or you can buy ready made cloches see the link below
We have found that adding a simple irrigation such as a leaky hose or drip in increase crop production by around 20 to 30 percent and save water compared with watering by hand.