Do you think this is down to my legs getting used to the different running style.
Yes.
I switched to fore then midfoot striking, and ran VASTLY better as a result.
The heel strike thing – well the real problem imo is heel striking *too far in front* which is what I was doing. This may be what you were doing – sticking your leg out, striking with your heel and rolling onto your foot like you do when you walk. This is bad form because your leg is braking your forward motion all the time.
If your foot is landing underneath your body then you’ll be fine. Personally I think midfoot striking is an easy way to do this, and it didn’t take me long to convert completely. Running now the old way feels awful.
the most prevalent fault people have IMHO is overstriding rather than foot strike
Or, what he said. However overstriding and heel striking are related.
SOME people also find that using thin flat shoes helps – because heel striking in front of your body becomes very difficult, so you end up not doing it. In the same way that you can’t really do it if you were to run barefoot.
Plenty of youtube videos about running style.