Convertible car seat (UK)

So my 5 month old hates the car. Others who have had the same issues have suggested changing his baby car seat which goes on the pram and getting a convertible car seat. Ideally I would like it rear facing as long as possible and isofix but that's not a must. I did like the look of the Joie i anchor but after reading reviews have decided against it because the lack of head support when the baby sleeps, not that mine ever sleeps in the car, just screams. Dont really want to spend more than £200. Any recommendations and the reasons why would be appreciated. It may not work but at least it will last a few years so not too much of a waste of money. TIA