The 92 and 99 day cancellation reflected the fact that there were 2 slightly different types of renewal mechanism for Nominet domains, one of which required a final 7 day warning letter before deletion (hence plus 7 days). 
I can't remember exactly what the difference was between the two, but as reported above it is now standardised on 92 days, unless the deletion is held up for a variety of reason, in which case it can drop any time up 
until years later.
Don't believe me? Check out this beauty - it's been suspended since March 2006 and still hasn't deleted... 
GardenerTravel.co.uk Whois Lookup
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