Thanks for the heads up on those blades. Might buy one to try.
It is a cheap saw alright though. It's a B&Q 'power' branded one I got from them for £50 in a sale, but the same machine is also sold as draper and all sorts of other common brands.
I have done a load of setup after watching videos and fitting the new better blade but could be something still not quite right I guess. Wondering if even insufficient tension could be causing it but don't want to overtighten it.