For a bird that will spend several hours outside in the room every day, a cage might do - 48 inches by 24 inches by 24 inches or thereabouts. Length and width matter more than height. Fancy circular or tall cages may look nice in your living room but are not good for birds. Think in terms of £120 upwards for a good cage on a movable stand - also try Northern Parrots on www.24parrot.com .
Never buy a "starter pack" cage sold in pet shops. They are always too small. Many pet shops sell really lousy cruelly small cages so do careful research online, remembering whether you are looking at inches or centimeters. Always buy the biggest you can afford. Good quality lasts longer. A cage that opens at the top is useful so a bird can sit up there. The bar spacing should be 15 mm or less - anything bigger and the budgie will get its head stuck. Some of the bars should be horizontal not vertical - better for climbing.
