Hi ​@Irishgripper, as far as I know Strava can't do it (but maybe someone will correct me - maybe something can be done yet on Garmin side before the import), however, there are some 3rd party tools that could help:

https://support.strava.com/hc/en-us/articles/221258108-Merge-or-Combine-Activities
 

Also, there's a related feature request that you might want to vote for: 

ignore this… typo

That wouldn’t work, but most Garmin watches can broadcast the heart rate and the Edge can receive that so you’ll have all the data in the Edge activity.

Are you using data from the Edge that you wouldn’t get from the watch?  One idea would be to just upload the watch data and not the Edge.  The watch should be recording pretty much all the same stuff the Edge does plus it will have the heart rate included.  You can still use the Edge to see the ride statistics while riding, just don’t upload from that device.  

Many thanks for the replies with various suggestions. I think I will initially try to get my Edge to pick up heart rate data from my Garmin watch then when Edge uploads to Strava hopefully everything will be there. If that fails then I’ll try recording everything on the watch & then upload directly to Strava from the watch. Just makes my Edge slightly superfluous.