Kiddicare have 40% off the The Super Car seat which is currently on sale for £29.99. We've had this car seat for over 2 years now, and still love it and it's going strong for us, so it does have my personal recommendation.
The Super Car seat is a group 1/2/3 car seat suitable for children from 9mths - 11 years. It fixes into the vehicle forward facing with the cars 3-point seat belt. The car seat comes complete with a 5-point safety harness and chest and crotch pads, it has an height adjustable head-rest so it will grow with your child and padded arm rests for your child's comfort whilst travelling.
The seat is lightweight and will fit most vehicles.
Another really useful thing is that the car seat cover removes easily for cleaning.