No party has to put a candidate up in every constituency and, as you say some cannot because of the cost.
However to deliberately withdraw from a constituency and tell your members who to vote for in your place is one step further, and I, for one, am not prepared to do that.
If SW Surrey chooses to do so that is their business. I do not live in that constituency. But if I did, I would not vote for the candidate just because I was told my party's candidate had decided not to stand and I should vote for a named individual of another party in their place.
I think the whole subject of election expenses is due for revue. Now we are having so many of these presidential style elections for various posts, from Police Commissioners to Mayors, where decisions on candidates are made a year or more in advance and that person is campaigning from that point, much tighter regulations must come in
But to be honest I really cannot see any connection between my original email, your reply and the non-sequitor on mayoral election costs added on to your emaail. Were you out to catch me out on some point or another, although I cannot see how you could have been.