Guys..
I may be posting something that you already know, but I found the answer to my problem. Even though the battery showed over 12 volts and was left on an Oxford trickle charger which I guessed would keep my Yuasa battery in top condition, when I used jump leads off my zxr the PGM worked perfectly and therefore the battery must have been faulty.
New battery put in and bingo I get P-030 on the dash.
No more chattering and looking for bad earths or the like.
Thought I'd post it in case someone else with an MC28 suffers the same chattering when inserting their PGM card.