Bank hols day off in lieu

[Greengr]

Work term time only, 20 hours a week. Monday isn't my working day. Should I be entitled to time of in lieu for bank holidays that fall on a Monday outside of term time?

Only if your contract says so. A lot of people here will say the answer is yes, the real answer is "only if your contract says so". For example, when DH was a teacher working Wed/Thu/Fri, he never got it adjusted for the inset days or bank holidays - that's the norm.

What does it say about your holiday in the contract?

Eg in some places you wouldn't get full bank holiday entitlement you'd have to use your leave - does it say in that section what your bank holiday entitlement is?

All employees are entitled to paid absence for eight public holidays (pro-rata for part time staff) during each year, and any other designated public holiday, including:

New Year’s Day
Good Friday
Easter Monday
May Bank Holiday
Spring Bank Holiday
Late Summer Bank Holiday
Christmas Day
Boxing Day

If a standard working week is 37.5 hours and you work 20 hours term time only then based on your description I would think you get (20/37.5) x (38/52) x 8 bank holidays as your entitlement.

If there are more than 8 public holidays I think you'd have to check because the wording in your contract isn't clear. It says 8, then it also says "and any other" which could imply you get more if there are more.