During the life of your company can use either the full version Limited or the abbreviation LTD. You can interchange between these at anytime and use either version on stationery, websites, business cards and other business correspondence. You can also display your name in title case or capitals. Either version is legal and acceptable.
Ltd, LTD, Limited or LIMITED it makes no difference, the choice is yours. Please note that Companies House always record data in capital letters. They will not produce a certificate with lower case text.