Gosh, finding one's way round that web site is a right b****r, isn't it.
Having found form 1157 I note that it says:
Any of the ‘O’ items may be tested at the examiner’s discretion.
just as "training as necessary to pass the test" is effectively at the club's discretion.
So yes, in theory I could get away with no nav practice or testing at all, but that doesn't sound like a very good idea to me, and I'm sure it won't to the club, and I'm sure I wouldn't want to be flying with an outfit that thought I didn't need any nav revision after thirteen years of not flying.
(What a pity I'm not retraining with a cowboy outfit - I could save hundreds of pounds!!
)