They have a few different models, so I don't know exactly which one you mean, but in general no. It's a shame because they have lovely patterns but they just aren't the greatest as car seats. They need a better seat supplier! Their strollers are great if you did want to grab a bargain from their sale.
The all in one seats (from all brands, not just Cosatto) usually do not perform very well in crash testing unfortunately and some Cosatto seats have performed poorly in the past as well (though there's no crash test result on their currently sold seats, except the come and go i-rotate).
In terms of features, other brands are offering better for the same/similar price.
I've seen people have trouble with the harness as it's difficult to get a nice snug fit with it. I know they do have quite huge discounts on their sale but honestly - the models at £200/£250 you can get better seats for this price. The model at £150 I wouldn't recommend even at that price as it uses a top tether which is not ideal for rear facing, the instructions are confusing which increases the chance of accidental misuse and the rear facing position is only allowed to be used in the recline position which makes the seat take up a lot of space.
There are a few models that they do which are currently between the £150-200 budget which have a support leg and are probably OK - they are probably the best option if you're dead set on a Cosatto seat. But the belt fit when you use these seats in booster mode is quite poor, so it might be worth considering changing the seat when you get to that stage.
I have also heard some people say that they liked the prints when their child was younger but when they got to about 7+ they thought it was babyish and wanted to stop using the seat, so they ended up swapping it anyway - sometimes to a much less safe type of seat e.g. backless booster.
It sounds good to get one seat all the way up to age 12 but in practice it's usually better to buy for the stage you're in currently.