The Mamas and Papas Bop highchair is on special offer at Argos right now, reduced from £39.99 to just £18.99. That's less than half price!
The reviews on this one are a little bit mixed but it has scored 4.3 out of a possible 5 stars so it seems as though it'll do the job. Some customers have pointed out that the legs get in the way when you're not using it due to the angle of them, so bear that in mind if you're tight for space - it doesn't fold away. But plenty of other reviewers say it's a brilliant buy and represents great value for money. It's also easy to assemble and very easy to clean, based on the reviews.
Stock levels are very patchy for delivery - presumably this chair is particularly popular at the price - but if you can collect in person from your local store then you shouldn't have trouble getting hold of one. And you won't have to pay the £3.95 home delivery fee, either!