Thanks for all of your feedback & suggestions - it's been very helpful. I'm glad I'm not alone in thinking there must be a fix for it!! Fingers crossed :)
We have been having problems with our Grant Votrex Pro Internal Combi boiler since we moved into our recently renovated rental property in Nov 2016. Here is it's story - I'm hoping someone might have come across something similar, or that someone with better knowledge of boilers than me might be...