MP,
We recently had a student who could not complete his PPL QXC in one day due to inclement wx at the 2nd airfield. If he had got on with the job instead of hanging around for a couple of hours he would have completed the final leg. Instead, he had to get a taxi home.
However, as no definitive time scale seems to be written anywhere, we contacted Mike Grierson at the CAA's approvals dept to ask if it would be OK for our student to be ferried to his last airfield to complete the final leg of his QXC.
We were advised that the CAA would EXPECT the QXC to be completed within a 24 hour period. The only reason that this has ever been waived was when an aircraft went tech at one of the visiting airfields.
Not an answer to your specific question, but I would advise that you contact the CAA BEFORE setting off if you do not intend to complete the flight within 24 hours.
Regards
76