Car seat help

Aliya has pretty much outgrown her carseat so we need to get a new one for her.

The one we have in Mr S's car kind of comes apart in stages so that it grows with her - she's been in it since she was 2 and it eventually becomes just a booster seat, so will last her right up until she no longer needs a seat.  However it doesn't have Isofix fittings, which we would prefer as my car has Isofix points.

So the requirements are:

Isofix

5 point harness if poss although I know as she gets bigger the carset will evolve to just use the car seatbelt

She is 4, but quite small and only weighs just over 2 stone (hence still wanting a 5 point harness).

Can anyone help - I seem to be able to find isofix or 5 point, but not both together.

We're moving through the Maxi Cosi range - is there anything there (Priori/Tobi) that might work for you?

Haven't checked out Maxi Cosi yet - will go have a browse now, thanks Madonna!

Hmmm, no luck there.  They only do 2 seats past 3.5yrs and neither of them are 5 point or have isofix.  I think we are going to need to go for one or the other. 

So I guess my next question is which is the most important?  I guess Isofix as the 5-point bit she will outgrow pretty quickly anyway.