Sorry for the delay on this, things have been a bit too hectic recently to find some private time with my hobbie electronics 
I just tried this and it works a treat. Magic. Thank you very much for your help.
Unfortunately I haven’t got a clue what I just did. Would you be able to tell me what implications this change of the “buffer size” has on the sketch? This is because I’d like to make some further modifications and I need to know whether there are any new limits I need to work with!