I am delighted to report that during our lunchtime walk today, Polly trotted at heel along the lane home from the field completely hands free (my hands that is, lol!) I tucked her lead into my belt, told her what I wanted and she was eager to oblige. Prior to that we walked the last length of the field completely off lead with Polly walking to heel, staying close, waiting at the corner, being invited to go a little way on her own to play, then returning promptly to heel when called.
I'm starting to think the potential for walking to heel off lead may actually be a possibility for the future! I'm sure we've a long way to go before she walks like this with added distractions such as other dogs, but even so, could this is actually be a break through?!!!