Working from Home but required to go in 3-4 times a year to an office 80 miles away

I work permanently from home, so I assume this is classed as the Permanent Workplace (the office is 80 miles away). Work from home is why a took the job 3+ years ago. The reason for going into the office on those 3 or 4 occasions are for specific reasons such as annual results, training, handover of work - that kind of thing. Does this class the office as a Temporary Workplace and so get tax relief on this mileage claim? My employer wants me to get Business Insurance and class this as business mileage but I do not believe that this is correct.

Hi,
Please refer to guidance at Employment Income Manual EIM32075 - Travel expenses: travel for necessary attendance: definitions: temporary workplace
Thank you.