72 hr transit and L Visa?

Andrew, thanks for answering, however, I need to clarify...I will be flying to SHE on April 3, leaving SHE for Vietnam on 5, returning to She on 22 and staying there until May 2, when I will return to UK via FRA connection. Will my L type still cover the stay from 22 April to May 2 and will I be able to use the Transit G for the first couple of days?
Thanks