Here's our company policy on the matter:-

Your bank holiday entitlement is calculated as follows:

XX days (number of public holidays) x XX hours (weekly hours) divided by 5 days = XX hours

Please record and manage this locally with your manager based on the "rules" below :

For a public holiday that falls on your normal working day you should deduct the number of hours you would normally work from your local record. For example, if you work 5 hours on a day where a public holiday would normally fall, 5 hours should be deducted from your public holiday entitlement on your local record.

If you do not have enough bank holiday entitlement, then the additional hours need to be deducted from your standard vacation entitlement.

If a public holiday does not fall on your normal working day then you do not need to deduct any hours from your public holiday entitlement.

So for me, I work 33 hours out of a nominal 37 with my usual days being Tue/Wed/Thu/Fri (i.e. no Mondays).

My holiday allowance is 28 days (yes, not including bank holidays), but this is pulled down by 33/37 so that's 28 * 33/5 = 184.8h

There are then 8 bank holidays in the year, so I get a maximum of 8 * 33/5 = 52.8h towards covering those.

The important point to note, that may not be clear from the above quote, is that any unused holiday in my "public holiday entitlement" bucket is gone at the end of the year, I can't borrow from it or use it for normal vacation.

If I worked 50% hours and all of the public holidays fell on days I worked then I'd have to use my own personal holiday entitlement to cover half of them, annoying but fair.

If I worked 50% hours and none of the public holidays fell on days I worked then I simply don't have to work them, but can't use the unused "public holiday entitlement" bucket for time off at other times.

In reality, no-one at our place cares or looks too closely at it at all. If I did work a Monday (I used to before I switched from Friday off) then I just used to have all of the Bank Holidays off just as everyone else did, never a worry that my BH entitlement might not cover it.

I also buy 66 hours (2 weeks worth of my 33h week) holiday a year via salary sacrifice so my total is 250.8h/year. At 33h/week that's 7.6 weeks, plus every bank holiday off. *smug*