Flybywyre
NDB Holds are necessary at airfields without radar or indeed for NDB approaches themselves - have a look at the Approach plate for Rwy 22 at Cranfield. Plymouth and Sheffield will be the same. I've also been the pax in a Fokker 100 when the radar was out at East Mids - again holding was necessary to sequence us and the UPS 767 below us.
Bookworm
ANO Sched 5 and Article 15 are the reading that you want
CM
[This message has been edited by Chilli Monster (edited 12 June 2001).]