The suburban buildout in Britain over the past 40 years has been enormous, between the natural increase and the skedaddle from the big urban centers (in part due to “immigration” / deliberate anti-british population replacement), with a large modernization of roads and highways making commuting ever more practical.
Britain already had a national rail system, but roads reach many more of the nooks and crannies where people can and do move now.
The UK estimates for the number of gigafactories needed to meet British demand alone looks, well, nuts, but it’ll probably pan out.
https://duckduckgo.com/?q=tesla+in+uk+reviewed
https://www.google.com/search?q=tesla+in+uk+reviewed

| Ethnic group | Population (2011) | Percentage of total population[19] |
|---|---|---|
| White or White British: Total | 55,010,359 | 87.1 |
| Gypsy/Traveller/Irish Traveller: Total | 63,193 | 0.1 |
| Asian or Asian British: Indian | 1,451,862 | 2.3 |
| Asian or Asian British: Pakistani | 1,174,983 | 1.9 |
| Asian or Asian British: Bangladeshi | 451,529 | 0.7 |
| Asian or Asian British: Chinese | 433,150 | 0.7 |
| Asian or Asian British: Other Asian | 861,815 | 1.4 |
| Asian or Asian British: Total | 4,373,339 | 7.0 |
| Black or Black British: Total[note 1] | 1,904,684 | 3.0 |
| Mixed or Multiple: Total | 1,250,229 | 2.0 |
| Other Ethnic Group: Total | 580,374 | 0.9 |
| Total | 63,182,178 | 100 |
They are 87% White British and quite frankly the Indians, Other Asians and Black (mostly Carribean) are well integrated in British society.
The only problems with minorities are with the Muslims
In terms of the Gigafactory, you are right, the UK has great public transport. Electric cars will just make it better for the last leg - most likely they will be rental by the minute cars (quite a lot of them already operate)