Hugmonster - the omission has been rectified. I guess it's down to experience - a bad experience with Abbott when I was younger! :-)
10W - thanks for the thoughts, it all seemed to be a little too far away!
I have now cracked it! The AIP appears to show coordinates as decimals eg SPEAR is 513434N 0004201E. In actual fact, these are degrees, minutes and seconds - 51 degrees, 34 minutes and 34 seconds. Converted to decimal with a divide by 60 of the minutes and 3600 for the seconds gives 51.57611 (and so on). An altogether more respectable result when thrown at the map.
Thanks all for your help!!