I have already submitted this to Garmin before I knew about this forum for reporting requests. I thought I would post so other users know that Garmin are aware and have said they have sent to the developer to make the correction - but have given no timescale.
On the activities page, if you hover your mouse over 'Av Speed (Av Pace)' or 'Max Speed (Max Pace)' it shows the metrics as 'Miles per Hour', this is incorrect, the data shown is in 'Minutes per Mile'.