@Gillian thank you for the response and advice, although my fault at not clarifying 100% in my post. I’m meaning that the newborn will have an isofix base and my 2 year old will keep hers (all being well) I’m looking at getting my almost 4 year old a slim car seat for the middle. Not that I’m looking for another isofix base, I need a narrow car seat. Again I appreciate the comment and it’s something we are looking at and measuring etc to see if we can fit a 3rd in the back but that’s why we’re looking into the slim designed car seats. We also have a ford ranger truck so our back has slightly more room than the average car but we still have our measurements to do. If things don’t go to plan we’ll get 2 smaller car seats for my older 2 and then the isofix infant car seat for my newborn. I appreciate the response thank you ☺️
Have a look at Car Seat Safety UK or Bump to Booster on FB. But a few points: 1) not all cars will allow you to get three across, especially those with the 'half' middle seats 2) you don't need isofix. Seatbelt install is just as safe. 3) most 'high street' seat so Joie etc are particularly wide.