Hi for vehicles in the UK it is possible to search for the number that have a license to drive on the road (MOT) through the website
https://www.howmanyleft.co.uk/
a search for Volvo 1800 for 2018 gives;
1800E 51
1800ES 45
1800 ES Auto 2
1800S 152
P1800 110
With the recent change in the UK law which means that vehicles older than 40 years (which meet certain criteria) no longer require an MOT this this data will be more difficult to get.
Looking at the data by year (see attached picture) the number of UK cars registered seems to be pretty stable over the last 17 years.
addendum The figures I quoted are for licensed (MOT) vehicles for those SORN'd (Statutory Off Road Notification) there is separate data which can bee seen when a particular model is selected on the website
https://www.howmanyleft.co.uk/
for example Volvo 1800S in 2018 there were 152 MOT'd and 96 SORN'd giving a total of 248.