Send the dealer the following letter (with the obvious corrections made) by Royal Mail's 'Signed For' service. (The letter must clearly show your name and address, his company's name and address and be dated. Those requirements are necessary if the letter has to be used as evidence in court action):
"Sir
On 15 June 2017 I purchased a Toyota Rav 4 (AB 05 CDE) from your company. I have subsequently been told by a Toyota main dealer that the vehicle needs a major repair (i.e. the supply and fitting of a new turbocharger unit). I therefore regard the vehicle as NOT FIT FOR PURPOSE (as defined by Section 10, Consumer Rights Act 2015)
I therefore exercise the RIGHT (given to me under Section 20 of the said Act) to REJECT the vehicle and DEMAND a FULL REFUND of the money paid to you in respect of the said sale.
I note that you state that you do not give refunds. I advise you that such a statement CONTRAVENES the provisions of Schedule 2 of the Consumer Rights Act 2015 (as brought into effect by Section 62 of the Act) and is therefore both UNLAWFUL and INVALID.
TAKE NOTICE that if I do not receive a full refund within SEVEN DAYS I will:
(a) refer the matter to Blogshire Trading Standards ; AND
(b) commence court action against you ; AND
(c) invite the local press to report upon the way that you conduct your business.
Yours faithfully"
Do NOT use the car. (If you do you'll lose the right to reject it).
If you need to contact Trading Standards, start here:
https://www.gov.uk/find-local-trading-standards-office
If you need to commence court action, start here:
https://www.moneyclaim.gov.uk/web/mcol/welcome