Spikey, I had the same problem as you although I had the best long handled shears. One day whilst using a strimmer with a swivel head I decided to try it on edging the lawn it worked a treat.
In time I learnt to put a plank down and walk along strimming the edge, this kept it straight and also cleaned the edge leaving soil instead of grass, no more problems after that.
I still use the long handle Spear and Jackson shears on weed and even bushes no bother at all.
Frank.