To be honest, if your ache is really bothering you I would go and see another physio, see if you can find one that specialises in running.
Most research done at the moment is indicating that the most efficient way to run is using a mid-forefoot strike rather than a heel strike. More than 10 years ago I decided to transition all my running over to a more fore-mid foot strike and have had much less overuse injuries since. If you look at the front of any big race the people there will have a fore-mid foot strike, check out Gebrsellassie here:http://www.youtube.com/watch?v=j_Yk1xeSLRk
and if it's good enough for him...
More specifically NO ONE ran with a heel strike before Mr Bowerman invented his new Nike shoes with lots of heel cushioning. You simply can't heel strike for long in 'normal' or pre-70s trainers, it's kinda ouchy. Bowerman invented his trainers based on his own assumption that it would make people faster, he carried out NO research to prove it would either make people faster or less injury prone, he just did it and with some clever marketing the world seems to have bought into it.
So, the Physio's statement that heel striking is the correct way to run is not true:
1) No one ran this way pre Bowerman
2) Bowerman's his new style of running was based on zip all research
3) Very few elite athletes in races heel strike
For me, I find the best way to check my running technique is when running on a paved/tarmac surface check it feels easy/smooth and sounds quiet (no foot slapping, scratching or scuffing noises on the ground).
That said, really hope your ache isn't too bad Chloe, could be something as simple as upping your training mileage quickly?
find the edge of the hurt envelope - and push...