I don't drive and IME it is actually a bit more useful to have the travel system as a non driver than you expect. Because if you get a lift/taxi somewhere but public transport back (or vice versa), it becomes a massive pain to lug the car seat around or ask the person to store it for you, so being able to just have the car seat be the pram is a real sanity saver.
I don't know what you know about car seats but essentially there are three stages of car seat you will need long term:
- Infant stage (rear facing, usually a carry type seat)
- Toddler stage (can be rear or forward facing, usually has a safety harness but may also have an "impact shield")
- Booster stage (booster seat with or without back and head protection which uses the adult belt)
Under European regulations these are known as Group 0/0+, Group 1 and Group 2/3 respectively. In all countries now you can get "convertible" seats which cover both the baby and toddler stage, making the infant carrier optional.
Toddler stage is the most tricky in terms of portability, cost, installation and so on, but also the most critical in terms of safety, particularly if they go into it quite early. It does pay to think ahead to this stage and have a strategy which includes it. You've always got overlap between limits of each seat for different stages, so I'd go with one or a mix of these three approaches (with EU suggestions and prices based on Germany - just to give a non UK idea)
The single most important factor that makes a difference in safety is direction of travel. Changing from rear facing to forward facing is a big step down in safety to the point that this is strongly not recommended (and may be illegal) before 15 months or 2 years in some places. The most basic rear facing seat will always be safer than the most advanced forward facing one. But all seats conforming to European/North American/Australian standards have passed safety testing and for children over about a year/18m old, a forward facing seat is still going to protect them in most situations. If you do very few journeys a year, it might be that "most" is enough compared to "almost all" given that the chance you will be involved in an accident at all is far lower than it would be for a child who is travelling in a car every day.
- Maximise practicality for minimal cost, compromise on safety.
- Longest lasting infant carrier you can find so the one with the highest weight limit or (more usually) longest shell, travel system compatible. Use to the very limit to maximise rear facing time.
e.g. Maxi Cosi Citi, €80
- Lightweight, easy to use or basic toddler seat
e.g. Urban Kanga (folds up), €150 / Britax Eclipse (plane approved), €110 / Cybex Juno, €120
As soon as child is the minimum weight and you trust them in a seatbelt:
- Detachable or lightweight but good quality booster seat
e.g. Maxi Cosi Rodi, €50
Consider getting the first two stages second hand (e.g. if there is a local expat network you trust) to save more money but be cautious doing this, especially if for example they have flown with the seat and it may have been bashed around.
- Maximise safety, compromise practicality
- Convertible seat which does rear facing past 13kg/29lbs
e.g. Joie Verso, €220
(That one actually converts to a booster, but if you found a different seat, you might need to buy an additional booster)
or
e.g. Joie Gemm, €65
- Highest limit rear facing toddler seat you can find
e.g. Britax Two Way Elite, €200
- Bubble bum/backless/cheap booster seat
- Extra-portable options to consider for higher cost or lower safety (worldwide)
- Doona (infant seat with pop out wheels) €330
- Nachfolger (inflatable convertible, allegedly suitable from birth) €349
- Urban Kanga (foldable toddler seat) €150
- Ride Safer Travel Vest (crash tested portable harness allegedly)
- Bubble bum (inflatable booster seat) €30