"all the necessary parts" ..... hmmm.
It could be a very good deal from a very reputable company, but the whole "reconditioned engine / gearbox" industry is fraught with scams, so be wary.
Is there VAT in that price or is it added on afterwards, or is the company turnover less than the VAT threshold, currently £75k I believe.
Oh, and mileage is spelt with an "e" and generally doesn't start with a capital letter and is normally followed by the word "warranty".