Most infant seats are compatible with most cars, though you might get an unsuitable angle if your seats are sloped. Unfortunately, this isn't really something you can check in the absence of a trained fitting. It might be worth contacting the retailer you order from directly and seeing if they are happy to accept returns if you're unhappy with the fit in your car. If you do this I'd also contact the manufacturer via email or social media and ask them if you can send them photos of the seat fitted in your car for feedback. You can also ask about the angle for a newborn, which you can check using a spirit level app on your smartphone.
Are you on Facebook? If so I would recommend joining Car Seat Advice UK - you can both search for your car model to see if anyone has posted before to see if there are any to look at/avoid, and/or make your own post asking for people's experiences. They might also be able to advise on home fitting, or recommend a local specialist you may be able to get phone support from now and in-person support if you need it in the future.
If you want one that is lightweight to carry, the most lightweight are:
Maxi Cosi Cabriofix
Maxi Cosi Coral
Maxi Cosi Citi
Maxi Cosi Tinca (yet to be released)
Joie Juva
Joie i-Snug
Nuna Pipa Lite LX
Venicci Ultralite
Britax Babysafe
Graco Snug Essentials
Nania BeOne SP (And rebrands, e.g. various own brand seats)
The list of seats which is compatible with Bugaboo pushchairs is as follows:
Bugaboo Turtle (made by Nuna)
With Maxi-Cosi adapters, all (carryable, infant) seats from the following brands:
Besafe
Cybex
Nuna
Maxi-Cosi
Recaro
And in addition with the same adapters:
Joie seats, except Joie Juva.
Axkid Modukid Infant with additional Axkid adaptors
Cosatto Dock
Venicci Ultralite
You can also get Britax (Click & Go) adapters for the Bee 5 which means you can also put on any Britax infant seat.
However I believe you take the seat unit off to fit the car seat on, so might be no use to you for taking door to door, unless you plan to leave the seat unit in the car. You can also sort of wedge/balance a car seat into the seat unit of the buggy of course, although it won't be very secure - but we've done this when we didn't have enough hands to carry everything.