can anyone please advise how I can get my 14week old pup to walk outside on a lead. He will walk indoors or in the garden fine on a lead but not when I take him out. I have tried titbits encouragement etc but nothing is working.

Don't rush him! It's scary out there. Have you tried carrying him a short way before putting him on the ground? Then let him have a good sniff around before you give a cheerful "Heel!" and set off.
:)