I'm a big Bumbo fan. But Bumbo Baby Sitters seem to divide parents. They either think they're indispensable or a total waste of space. And for something that you might end up thinking of as useless, they're not exactly cheap. But at this price - £20.98 at Amazon, down from £34.95 - trying one out is a bit more affordable.
Plus if it doesn't work for your little person, then the good news is that Bumbo Baby Sitters tend to re-sell for really good prices on Ebay so you might even make a profit if it is unused and kept in the original box.
Here's the blurb: "Now your baby can enjoy a comfortable upright sitting position from around 4 months with this South African designed Grobag Bumbo Baby Sitter. Simply pop the moulded bumbo baby sitter supportive shape on the floor and sit your baby inside. Because the material is soft, your babies body weight and pressure narrows the gap above their legs slightly so they sit safely and securely without the need for fiddly, restrictive straps. Your little one will love the independence to look around and use their hands."
As I've said, I loved this and it worked wonders with my eldest child who wanted to be up and at the world long before he was able to support himself when sitting, so this was perfect. We even used it as a highchair and you can get a tray table to attach to make that even easier. In contrast my youngest babe despised the bumbo so we ebayed it pretty sharpish. There's no guaranteeing that this will work for your babe but this is the best price I've seen these at, so if you're tempted I'd recommend stocking up while the price is low because I doubt they'll hang around at this price for long.