OMG! My new battery arrived today. I got home from work and went straight at it and this time I managed to change the primary code to something more personal! Excellent!
I wonder if having the battery made the difference?!
Next move is to replace the bell box battery...
To answer your question;
I DO plan to upgrade my alarm system for something more modern, but after moving house and haemorrhaging money for months as a result, the funds just aren't there right now. Next year probably.