After several years suffering the *frustration of the very slow load time on my MacBook Pro 2012 Spotify now works like it should and I am very pleased with myself. "Why?" I hear you ask - well I installed a SSD is all. The MacBook is very happy and we are the best of friends again.
On a side note my mail app now loads immediately too - it was pretty laggy - also a couple of apps that had begun misbehaving eg.Photoshop have also recovered their mojo. All this time I guessed it was a connection/software issue (Spotify worked fine on my iPhone SE) turns out for me anyway that it was hardware.
*I'd tried all the suggestions I'd found here and elsewhere on the web