If the ideal bank holiday for you is a long weekend in the garden May really is the best time to be busy. In many parts of the country May is a month in which more tender plants can be put outside, we should be frost free by the end of May, but it is always an idea to have a fleece or cloche handy.
May is also a good time to think about the "Chelsea Chop" which is a great way of stopping some plants getting too big and “leggy”, and help other plants by staggering their flowering times. It’s called the Chelsea chop as it should be done around the time of the Chelsea Flower Show in late May. But it is important not to chop too early in May if plants have just not reached the right growing stage because of a cold spring. If you haven't used the Chelsea Chop before it is really worth considering and there are several YouTube videos to help you.
If you are looking to grow some veg this year in your St Albans or Harpenden garden now is the time to get your more hardy veg in like Broad beans, Runner beans, Peas, Onions ,Garlic and carrots.
Some other varieties are best to plant under glass and / or delay planting out until Early June, like the more tender vegetables French beans, Squashes, Cucumbers, courgettes and chillies. But May really is tomato time! It's a good time to buy plants to grow on in the greenhouse, or when all risk of frost has passed put your tomatoes out in a sunny spot.