Automatic Gmail Out of Office based on Google Calendar Entry (Google Script)

I only work 4 days a week. Sometimes the day I take off varies. Sometimes I take more time off.
I would like to have my Gmail automatically enable and disable it's native out of office based on a key phrase, i.e. "OOF", in my Google calendar events (which may be in one of multiple calendars, not necessarily my primary calendar).

The Out of Office message should turn on 5pm of the first WORKING day BEFORE an OOF event, and turn off midnight of the last day with an "OOF" entry.

The Out of Office message should include text stating the date I'll be back in the office (by incrementing through my calendars until the first day is found that:
- Does not contain an event containing the text "OOF"
- AND is not a weekend day
- AND does not contain the text that describes any of the England public holiday days contained within this ICS file: https://www.gov.uk/bank-holidays/england-and-wales.ics

See attachment for examples of the intended logic.

Ideally the out of office message would include my signature (this is just an image and formatted text (not HTML). This is not critical though - please advise in your proposal what you can achieve.

The code in some of the examples and links in this thread might be of use: https://webapps.stackexchange.com/questions/79963/can-i-set-gmail-out-of-office-replies-for-every-week-recurring