First of all you don't need to move her out of her baby seat if she still fits into it
You can keep using it until she meets either the weight or height limit or her head is starting to come over the top of the seat.
Secondly I would strongly consider RF at LEAST to age 2, it makes quite a significant difference at younger ages. Legally the minimum for FF is 16 months, but every extra month RF is of benefit. Toddlers don't really question whether they are supposed to be RF or FF if you don't give them the option, so you don't need to worry about her "tolerating" it - she has been fine up until now presumably, and that is not likely to suddenly change if she doesn't know any different. It is quite common to RF up to about age 2-3 (or longer!) these days, so lots of toddlers do this and it's not an issue.
Do you already have the base for the Pearl 360 Pro? It will be very expensive if you don't already have the base and IMO not worth spending £520 on.
For the £299 I would suggest comparing with Britax Dualfix M Plus (£269 at John Lewis) or Cybex Sirona Gi i-Size which is £224 at Mamas and Papas. These are quite similar to the Maxi Cosi but slightly more roomy for the child and better leg room and larger weight limit. I would probably go for the Britax if you're sure you're likely to FF, because Britax do FF seats well.
You could also look at some dedicated ERF options as FamilyAreEverything says - these have even better leg room, though you do lose the FF option.
If you were looking at the whole £520 budget, you might want to look at something like Axkid One2 which has much easier installation and good leg room but the benefits of ERF - again this is a rear facing seat only, but a lot of the things which put people off ERF are absent in this seat. You can slide it on rails to get the balance you want between child leg room and front seat space, it's light, it's easy to fit and it lasts a long time.
Or if you are keen to FF ASAP, you could keep LO in the baby seat for as long as possible until it's totally outgrown (minimum 15m+ but ideally 18m+) and then look at changing to the Cybex Anoris T, or Britax Trifix 2 if you wanted something cheaper, as these are the best-rated forward facing seats for safety and they aren't trying to do two jobs like a spin seat is.