You can get this seat at this price if you choose the black colour. Tesco have them at £24.99 excluding the delivery charge.
I just ordered one myself, as at this price it's a good buy really.
Polisport Joey Child Seat
Features of Product Perfect ergonomics for your child, 3 point safety belt, adjustable foot rests, fixing brackets fits most tube styles 28-35mm, maximum child weight 22kg
Product Depth 30 cm
Product Height 74 cm
Product Width 33 cm