An interesting question.
Regarding your time off as OML, I believe your company should be accruing the holiday as if you were employed normally. I searched the web for confirmation, and found this (scan down the page) from the DirectGov pages that seems to confirm the same.
http://www.direct.gov.uk/en/Employment/Employe es/WorkingHoursAndTimeOff/DG_10034642
Regarding your time off as AML, I believe this is down to company policy. This period off is much the same as asking for time-off unpaid from one's employment - it is 'optional'. As an HR Manager in the past, I have previously operated a policy of declining to accrue staff holiday for periods of unpaid leave. I cannot find any info on Direct Gov or other places to suggest there is a statutory obligation on your company to accure you holiday time for this period off.
Hope that helps. BM