I got George's highchair 2nd hand its the Chicco happysnacker 'seventies' style, again retails about £100 (ouch!) and paid £30 for it in new condition on a local for sale/swop site on my facebook.
George is just learning to sit unaided but is really safe in the chair, and it has an extra leg rest setting for small babies before they can sit properly and rest their feet.