Yes gardening is a great way to fill the time. And eating something you have grown yourself always tastes nicer. 🙂
Looking at Argos they have a walk in Greenhouse for about £50, it depends how much room you have and how much you want to grow that needs to stay in the greenhouse all year. Maybe a smaller one if it is stuff that can later go outside. Good to get the cheaper plastic version first then if it works ok and you enjoy it you could think about a more permanent fixed glass one in the future..