For sale is my trusty folding bike seat, the Bobike Junior.
This is great for kids that have outgrown a standard bike seat, i.e.. most kids over about 5 years old.
The seat provides support when sitting on the back of a bicycle unaided. The Bobike Junior can carry a weight up to 35 kilograms (approx. age 8 to 9 years old). The seat is equipped with a lap belt so that your child can not stand on the back of the bike. When the seat is closed the seat is a multifunctional carrier with a convenient bag bracket. You can fold the backrest down and up again by pressing the button on top of the seat back. You can easily adjust the footrests to the length of your child's legs, giving you years of usage as your child develops.
I used this to ferry a (tall for his age) 4 year old to nursery, and also carried him at age six on a cycle tour around Norfolk. Has also been used on trips around town and leisure journeys where route was not suitable for child on their own bike, or journey too long. Handy also for when a tagalong cannot be used easily, e.g.. train based journeys.
These seats are retailing for £72 new currently. Looking for £40. PM me if interested or you need further information. Please see images below for an idea of how seat looks folded, unfolded, and how it fits to the bike,