The passenger car market in the UK noted its weakest September since 1998 with 215,312 new registrations (down over 34% year-over-year). Supply issues caused by semiconductor shortages have significantly affected car sales.
The brightest star of the show is battery-electric cars, which noted a record month (32,721 units and 15.2% market share), which allowed for setting a new all-time record also for all plug-ins - 46,605 (up 36% year-over-year).
The Society of Motor Manufacturers and Traders (SMMT) notes that the plug-in market share improved to 21.7% (on of the highest result ever).
Plug-in electric car registrations in the UK – September 2021
- BEVs: 32,721 (up 49% year-over-year) at market share of 15.2%
- PHEVs: 13,884 (up 12% year-over-year) at market share of 6.4%
- Total: 46,605 (up 36% year-over-year) at market share of 21.7%

So far this year, more than 212,000 new passenger plug-in cars were registered in the UK, reaching an average market share of 16%.
Sales YTD:
- BEVs: 125,141 (up 88% year-over-year) - market share of 9.5%
- PHEVs: 87,040 (up 105% year-over-year)- market share of 6.6%
- Total: 212,181 (up 95% year-over-year) - market share of 16.1%

More details, including also other types:

Top models
The Tesla Model 3 happened to be the most registered model in September (6,879), which already happened a few times before, usually in the last month of a quarter when the manufacturer delivers its cars.
Despite those successes, the Model 3 is not yet able to enter the top 10 year-to-date. We estimate that the Model 3 is not far behind, with at least 18,932 units sold so far this year (6,585 in March, 5,468 in June and 6,879 in Septemer).
Unfortunately, the SMMT does not provide ranking for plug-ins so we can't extract more data right now.
Kia reports that during the first nine months has sold 10,063 all-electric cars (Niro EV and Soul EV). In Q4, the company will start deliveries of the EV6.

More sales reports
Source: SMMT