[OWDavid]

B, C, D & E are correct. You are allowed to continue play with the provisional ball whilst walking to the original position, so long as NO shots are played from in front of where the original ball is deemed to be.

With A, you are quite correct in that due to nominating a PROVISIONAL ball from the tee, until such time that you state that the Provisional is now in play, your first ball is still active until the end of the 5 minute search or it is found OOB. If after seeing that the Provisional ball was so good you wished to continue with that one rather than look for the first, you should have, after leaving the tee area, made it totally clear to all parties that you were deeming the original ball LOST. Obviously if you do not do this and someone finds it within the allotted time you are bound to play it no matter how gruesome the lie may be.

That's exactly what I'd always been told to do, declare verbally that you're assuming the ball to be lost, but found something on the R&A's website in the rules explorer at the following link:-

http://www.randa.org/en/Rules-and-Am...7&subRuleNum=1

If you scroll down to the bottom of Rule 27-1 there's an FAQ section where the question, "Can a player verbally declare his ball to be lost?" is asked. The reply is:-

A player cannot render a ball lost by declaration. A ball can only be considered lost when:
a) it is not found or identified by the player within 5 minutes after the player's side or his or their caddies have begun to search for it; or
b) the player has made a stroke at a provisional ball from the place where the original ball is likely to be or from a point nearer the hole than that place (See Rule 27-2b); or
c) the player has put another ball into play under penalty of stroke or distance under rule 26-1a, 27-1, or 28a; or
d) the player has put another ball into play because it is known or virtually certain that the ball, which has not been found, has been moved by an outside agency (Rule 18-1), is in an obstruction (Rule 24-3), is in an abnormal ground condition (see Rule 25-1c) or is in a water hazard (see Rule 26-1b or c); or
e) the player has made a stroke at a substituted ball

From what I read into that, no-one can verbally declare a lost ball, it's only deemed lost when one of the actions mentioned above is taken, and that the 5 minute rule only applies is the player, a member of their team, or one of their caddies, starts looking for the ball.

If you go to that link, there's a section to the right titled "Decisions related to rule 27-1" that has some queries sent in by people and the appropriate ruling. Makes interesting reading.