Taking car to UK

Hi, I hope someone can help me. My parents moved from the Uk to Ireland 2 years ago but have decided to move back to the UK. My dad bought a car here that he loves and we were thinking it would be simple to take it to the uk with them. I ordered an import pack so we could start filling it in and it said that you can not drive your car back you have to have it on a transporter. My dad then rang them explaining that it was a used car and could he not just drive it and register it in the uk and the women he spoke to was adamant that you can not drive your car on foreign plates if planning to move to the uk unless you pre-book an mot and drive from ferry port to test center. This is not possible as they arrive in the uk at 11pm at night (she said it has to be done the same day you arrive). When researching the move for my parents i did not come across this rule anywhere. As far as i could tell you drive your car to the uk, get an mot, get insurance using the vin numbe and tax and wait for your new registration after you fill out the import pack. Sorry for the long post but could someone who has done this recently clarify this please. Thanks very much.