We are about to move back to the UK with a 6yo who was born here. I'm assuming it's the same in the UK but there are loads of places over here that hire out the baby capsules that you need for a 0-8 month old as nobody buys them. When you get here, there are lots of places that make a fortune selling all the infant car seats. There are several specialist places but stores like Kmart and Target are everywhere and are selling 2/3rds of the same brands for a lot less.
You might not like the idea but it would be worth considering ebay or Gumtree when you are looking for a baby seat. Once my son grew out of the infant seat my wife had researched and decided on (that cost us AU$350), i could not give it away. Nobody wants a 2nd hand baby seat. It was in perfect condition, no stains, marks or issues. We ended up giving it to a charity shop as we just could not sell it for any money.
Just my 2c worth