You are doing one of the only effective methods by pruning. Aside from pruning look over the plant every week and if you see scale scape it off with your fingernail or a small and rather dull penknife. Oil or soap based treatments are effective only for immature " crawlers" so that is a matter of random timing only determined by observation. Scale insecticides are not too effective from my experience with house plants which is limited.

Systemics work slowly at best, and shouldn't be used on blooming plants, to protect the bees. I have had good results with a miture of surfactant and carbaryl, but I understand that carbaryl is not available in the UK. Not sure what to substitute.

Thank you both. I'll keep a look out during the season.
Might try painting on meths if there are too many to pick off as it works for scale insects on cacti. Hope I've got rid though!