Well, it's all done now, 4 Infinity's in the motor and given I know very little about in car audio (more of a home cinema man) I thought it was quite an easy task.
The hardest bits are cutting the bloody flanges off the Autoleads adaptors with a tiddly little hacksaw and no bench (my own fault I suppose!) and getting the speaker covers off. The rest is a doddle!
To answer agplant, there is a specific point where you can get the screwdriver in further for leverage, at the bottom (7 o'clock ish) and as recommended I used a bit of thin cardboard (from the adaptor packaging) behind the screwdriver so I didn't harm the door plastic.
I slightly scratched the first one as I hadn't figured out the above but the rest all came off without incident.
Will try to extract pics from my phone, but no promises of good photography!