You might find it better to buy separately. Most 3-in-1 type pushchairs (carrycot/parent facing/world facing) have car seat adapters which take a range of brands, if they say it's compatible with Maxi Cosi or Cybex and the adapters look like a chunky 3D letter "U", it's the universal type adapters and you can use them with any infant car seat from Maxi Cosi, Cybex, Nuna, Joie, Britax, Avionaut or Besafe. This gives you a better choice of prams and means that you're not paying an inflated bundle price. You could also consider second hand prams because they are much cheaper.
The cheapest swivel car seat and base set I can find currently is Kinderkraft i-Lite with the Endura base. That seems to use the same type of adapters. I know nothing about the car seat, but they are a reasonable enough brand and do the job. The set is £169 on amazon currently. Kinderkraft make very good travel systems for the price.
If you want a more premium car seat Amazon have deals at the moment on Cybex Cloud G taking it to £300 with Base G, or Maxi Cosi Pebble 360 with Familyfix 360 base for about £270. The Cybex lasts longer and has a reclining function.
Actually this would be a great set if you add the Maxi Cosi Familyfix 360 base to it for £140. It has the Cabriofix S car seat, which is retired but is compatible with the 360 base (just not the Pro version) according to older compatability lists: https://www.amazon.co.uk/Maxi-Cosi-Zelia-prams-travel-system/dp/B09ZLVP6ND/
Worth noting Maxi Cosi Pebble S is not compatible with Familyfix 360 base.
Another way to save money on the car seat part is considering whether you actually want a swivel base, because arguably with the baby seat it's not really needed. It often adds about £80-100 to the price compared with a non spinning base, or £150-200 compared with no base, which I think is a lot if you'll only use it for a short time.