Do you live in a city centre? If so, you might find that a W123 doesn't meet the regulations if a Clean Air Zone (CAZ) is introduced (or already exists). Currently, these are already in place in London and Bath, with plans to roll them out across numerous UK cities including Leicester, Birmingham, Manchester and Edinburgh. If they follow the same format as London's Ultra Low Emission Zone (ULEZ), cars with historical status (over 40 years old) will be exempt from charges. Otherwise, older Mercedes models like the W123 are unlikely to be outlawed. You'll need to be prepared for high maintenance costs running one as a daily driver but, on the flip side, a good one is unlikely to depreciate.