Thanks for the replies, they have been very reassuring. My contract is 40 hours a week. The office didn't change location, it's been in the same location since I joined the company...I moved across the country, but kept my position, working from home, as they could not replace me. Since I moved I've only ever gone into the office during leave, when I was visiting family in the area, at my own cost, or to attend a particular meeting (perhaps once a year, not regular, but when a manager visited from overseas perhaps). I've never worked from the office since moving away.
I have had three children since moving away, my last maternity leave lasting just six weeks (back to work in February 2014) and I have been pressed to work from the office as I described since around August/September. I advised the manager in question that had they pressed this requirement prior to my maternity leave I would have had to take the full amount of leave available, hence they left it for a while and are back on the case now, as it would be a year after I gave birth to my daughter/maternity leave would have ended. Not sure if this helps but thought it might be relevant.
Thanks again.